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doc/Makefile.am
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@ -18,22 +18,6 @@ man_MANS = \
taler-exchange-benchmark.1 \
taler.conf.5
AM_MAKEINFOHTMLFLAGS = --no-split --css-ref=docstyle.css --css-ref=brown-paper.css
DISTCLEANFILES = \
taler-exchange.cps \
taler-exchange.dvi
info_TEXINFOS = \
taler-exchange.texi
extra_TEXINFOS = \
fdl-1.3.texi \
agpl.texi \
syntax.texi
EXTRA_DIST = \
coding-style.txt \
$(man_MANS) \
$(extra_TEXINFOS) \
docstyle.css \
brown-paper.css \
exchange-db.png

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doc/agpl.texi
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@ -1,698 +0,0 @@
@c The GNU Affero General Public License.
@center Version 3, 19 November 2007
@c This file is intended to be included within another document,
@c hence no sectioning command or @node.
@display
Copyright @copyright{} 2007 Free Software Foundation, Inc. @url{http://fsf.org/}
Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.
@end display
@heading Preamble
The GNU Affero General Public License is a free, copyleft license
for software and other kinds of works, specifically designed to ensure
cooperation with the community in the case of network server software.
The licenses for most software and other practical works are
designed to take away your freedom to share and change the works. By
contrast, our General Public Licenses are intended to guarantee your
freedom to share and change all versions of a program--to make sure it
remains free software for all its users.
When we speak of free software, we are referring to freedom, not
price. Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
them if you wish), that you receive source code or can get it if you
want it, that you can change the software or use pieces of it in new
free programs, and that you know you can do these things.
Developers that use our General Public Licenses protect your rights
with two steps: (1) assert copyright on the software, and (2) offer
you this License which gives you legal permission to copy, distribute
and/or modify the software.
A secondary benefit of defending all users' freedom is that
improvements made in alternate versions of the program, if they
receive widespread use, become available for other developers to
incorporate. Many developers of free software are heartened and
encouraged by the resulting cooperation. However, in the case of
software used on network servers, this result may fail to come about.
The GNU General Public License permits making a modified version and
letting the public access it on a server without ever releasing its
source code to the public.
The GNU Affero General Public License is designed specifically to
ensure that, in such cases, the modified source code becomes available
to the community. It requires the operator of a network server to
provide the source code of the modified version running there to the
users of that server. Therefore, public use of a modified version, on
a publicly accessible server, gives the public access to the source
code of the modified version.
An older license, called the Affero General Public License and
published by Affero, was designed to accomplish similar goals. This is
a different license, not a version of the Affero GPL, but Affero has
released a new version of the Affero GPL which permits relicensing under
this license.
The precise terms and conditions for copying, distribution and
modification follow.
@heading TERMS AND CONDITIONS
@enumerate 0
@item Definitions.
``This License'' refers to version 3 of the GNU Affero General Public License.
``Copyright'' also means copyright-like laws that apply to other kinds
of works, such as semiconductor masks.
``The Program'' refers to any copyrightable work licensed under this
License. Each licensee is addressed as ``you''. ``Licensees'' and
``recipients'' may be individuals or organizations.
To ``modify'' a work means to copy from or adapt all or part of the work
in a fashion requiring copyright permission, other than the making of
an exact copy. The resulting work is called a ``modified version'' of
the earlier work or a work ``based on'' the earlier work.
A ``covered work'' means either the unmodified Program or a work based
on the Program.
To ``propagate'' a work means to do anything with it that, without
permission, would make you directly or secondarily liable for
infringement under applicable copyright law, except executing it on a
computer or modifying a private copy. Propagation includes copying,
distribution (with or without modification), making available to the
public, and in some countries other activities as well.
To ``convey'' a work means any kind of propagation that enables other
parties to make or receive copies. Mere interaction with a user
through a computer network, with no transfer of a copy, is not
conveying.
An interactive user interface displays ``Appropriate Legal Notices'' to
the extent that it includes a convenient and prominently visible
feature that (1) displays an appropriate copyright notice, and (2)
tells the user that there is no warranty for the work (except to the
extent that warranties are provided), that licensees may convey the
work under this License, and how to view a copy of this License. If
the interface presents a list of user commands or options, such as a
menu, a prominent item in the list meets this criterion.
@item Source Code.
The ``source code'' for a work means the preferred form of the work for
making modifications to it. ``Object code'' means any non-source form
of a work.
A ``Standard Interface'' means an interface that either is an official
standard defined by a recognized standards body, or, in the case of
interfaces specified for a particular programming language, one that
is widely used among developers working in that language.
The ``System Libraries'' of an executable work include anything, other
than the work as a whole, that (a) is included in the normal form of
packaging a Major Component, but which is not part of that Major
Component, and (b) serves only to enable use of the work with that
Major Component, or to implement a Standard Interface for which an
implementation is available to the public in source code form. A
``Major Component'', in this context, means a major essential component
(kernel, window system, and so on) of the specific operating system
(if any) on which the executable work runs, or a compiler used to
produce the work, or an object code interpreter used to run it.
The ``Corresponding Source'' for a work in object code form means all
the source code needed to generate, install, and (for an executable
work) run the object code and to modify the work, including scripts to
control those activities. However, it does not include the work's
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programs which are used unmodified in performing those activities but
which are not part of the work. For example, Corresponding Source
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The Corresponding Source need not include anything that users can
regenerate automatically from other parts of the Corresponding Source.
The Corresponding Source for a work in source code form is that same
work.
@item Basic Permissions.
All rights granted under this License are granted for the term of
copyright on the Program, and are irrevocable provided the stated
conditions are met. This License explicitly affirms your unlimited
permission to run the unmodified Program. The output from running a
covered work is covered by this License only if the output, given its
content, constitutes a covered work. This License acknowledges your
rights of fair use or other equivalent, as provided by copyright law.
You may make, run and propagate covered works that you do not convey,
without conditions so long as your license otherwise remains in force.
You may convey covered works to others for the sole purpose of having
them make modifications exclusively for you, or provide you with
facilities for running those works, provided that you comply with the
terms of this License in conveying all material for which you do not
control copyright. Those thus making or running the covered works for
you must do so exclusively on your behalf, under your direction and
control, on terms that prohibit them from making any copies of your
copyrighted material outside their relationship with you.
Conveying under any other circumstances is permitted solely under the
conditions stated below. Sublicensing is not allowed; section 10
makes it unnecessary.
@item Protecting Users' Legal Rights From Anti-Circumvention Law.
No covered work shall be deemed part of an effective technological
measure under any applicable law fulfilling obligations under article
11 of the WIPO copyright treaty adopted on 20 December 1996, or
similar laws prohibiting or restricting circumvention of such
measures.
When you convey a covered work, you waive any legal power to forbid
circumvention of technological measures to the extent such
circumvention is effected by exercising rights under this License with
respect to the covered work, and you disclaim any intention to limit
operation or modification of the work as a means of enforcing, against
the work's users, your or third parties' legal rights to forbid
circumvention of technological measures.
@item Conveying Verbatim Copies.
You may convey verbatim copies of the Program's source code as you
receive it, in any medium, provided that you conspicuously and
appropriately publish on each copy an appropriate copyright notice;
keep intact all notices stating that this License and any
non-permissive terms added in accord with section 7 apply to the code;
keep intact all notices of the absence of any warranty; and give all
recipients a copy of this License along with the Program.
You may charge any price or no price for each copy that you convey,
and you may offer support or warranty protection for a fee.
@item Conveying Modified Source Versions.
You may convey a work based on the Program, or the modifications to
produce it from the Program, in the form of source code under the
terms of section 4, provided that you also meet all of these
conditions:
@enumerate a
@item
The work must carry prominent notices stating that you modified it,
and giving a relevant date.
@item
The work must carry prominent notices stating that it is released
under this License and any conditions added under section 7. This
requirement modifies the requirement in section 4 to ``keep intact all
notices''.
@item
You must license the entire work, as a whole, under this License to
anyone who comes into possession of a copy. This License will
therefore apply, along with any applicable section 7 additional terms,
to the whole of the work, and all its parts, regardless of how they
are packaged. This License gives no permission to license the work in
any other way, but it does not invalidate such permission if you have
separately received it.
@item
If the work has interactive user interfaces, each must display
Appropriate Legal Notices; however, if the Program has interactive
interfaces that do not display Appropriate Legal Notices, your work
need not make them do so.
@end enumerate
A compilation of a covered work with other separate and independent
works, which are not by their nature extensions of the covered work,
and which are not combined with it such as to form a larger program,
in or on a volume of a storage or distribution medium, is called an
``aggregate'' if the compilation and its resulting copyright are not
used to limit the access or legal rights of the compilation's users
beyond what the individual works permit. Inclusion of a covered work
in an aggregate does not cause this License to apply to the other
parts of the aggregate.
@item Conveying Non-Source Forms.
You may convey a covered work in object code form under the terms of
sections 4 and 5, provided that you also convey the machine-readable
Corresponding Source under the terms of this License, in one of these
ways:
@enumerate a
@item
Convey the object code in, or embodied in, a physical product
(including a physical distribution medium), accompanied by the
Corresponding Source fixed on a durable physical medium customarily
used for software interchange.
@item
Convey the object code in, or embodied in, a physical product
(including a physical distribution medium), accompanied by a written
offer, valid for at least three years and valid for as long as you
offer spare parts or customer support for that product model, to give
anyone who possesses the object code either (1) a copy of the
Corresponding Source for all the software in the product that is
covered by this License, on a durable physical medium customarily used
for software interchange, for a price no more than your reasonable
cost of physically performing this conveying of source, or (2) access
to copy the Corresponding Source from a network server at no charge.
@item
Convey individual copies of the object code with a copy of the written
offer to provide the Corresponding Source. This alternative is
allowed only occasionally and noncommercially, and only if you
received the object code with such an offer, in accord with subsection
6b.
@item
Convey the object code by offering access from a designated place
(gratis or for a charge), and offer equivalent access to the
Corresponding Source in the same way through the same place at no
further charge. You need not require recipients to copy the
Corresponding Source along with the object code. If the place to copy
the object code is a network server, the Corresponding Source may be
on a different server (operated by you or a third party) that supports
equivalent copying facilities, provided you maintain clear directions
next to the object code saying where to find the Corresponding Source.
Regardless of what server hosts the Corresponding Source, you remain
obligated to ensure that it is available for as long as needed to
satisfy these requirements.
@item
Convey the object code using peer-to-peer transmission, provided you
inform other peers where the object code and Corresponding Source of
the work are being offered to the general public at no charge under
subsection 6d.
@end enumerate
A separable portion of the object code, whose source code is excluded
from the Corresponding Source as a System Library, need not be
included in conveying the object code work.
A ``User Product'' is either (1) a ``consumer product'', which means any
tangible personal property which is normally used for personal,
family, or household purposes, or (2) anything designed or sold for
incorporation into a dwelling. In determining whether a product is a
consumer product, doubtful cases shall be resolved in favor of
coverage. For a particular product received by a particular user,
``normally used'' refers to a typical or common use of that class of
product, regardless of the status of the particular user or of the way
in which the particular user actually uses, or expects or is expected
to use, the product. A product is a consumer product regardless of
whether the product has substantial commercial, industrial or
non-consumer uses, unless such uses represent the only significant
mode of use of the product.
``Installation Information'' for a User Product means any methods,
procedures, authorization keys, or other information required to
install and execute modified versions of a covered work in that User
Product from a modified version of its Corresponding Source. The
information must suffice to ensure that the continued functioning of
the modified object code is in no case prevented or interfered with
solely because modification has been made.
If you convey an object code work under this section in, or with, or
specifically for use in, a User Product, and the conveying occurs as
part of a transaction in which the right of possession and use of the
User Product is transferred to the recipient in perpetuity or for a
fixed term (regardless of how the transaction is characterized), the
Corresponding Source conveyed under this section must be accompanied
by the Installation Information. But this requirement does not apply
if neither you nor any third party retains the ability to install
modified object code on the User Product (for example, the work has
been installed in ROM).
The requirement to provide Installation Information does not include a
requirement to continue to provide support service, warranty, or
updates for a work that has been modified or installed by the
recipient, or for the User Product in which it has been modified or
installed. Access to a network may be denied when the modification
itself materially and adversely affects the operation of the network
or violates the rules and protocols for communication across the
network.
Corresponding Source conveyed, and Installation Information provided,
in accord with this section must be in a format that is publicly
documented (and with an implementation available to the public in
source code form), and must require no special password or key for
unpacking, reading or copying.
@item Additional Terms.
``Additional permissions'' are terms that supplement the terms of this
License by making exceptions from one or more of its conditions.
Additional permissions that are applicable to the entire Program shall
be treated as though they were included in this License, to the extent
that they are valid under applicable law. If additional permissions
apply only to part of the Program, that part may be used separately
under those permissions, but the entire Program remains governed by
this License without regard to the additional permissions.
When you convey a copy of a covered work, you may at your option
remove any additional permissions from that copy, or from any part of
it. (Additional permissions may be written to require their own
removal in certain cases when you modify the work.) You may place
additional permissions on material, added by you to a covered work,
for which you have or can give appropriate copyright permission.
Notwithstanding any other provision of this License, for material you
add to a covered work, you may (if authorized by the copyright holders
of that material) supplement the terms of this License with terms:
@enumerate a
@item
Disclaiming warranty or limiting liability differently from the terms
of sections 15 and 16 of this License; or
@item
Requiring preservation of specified reasonable legal notices or author
attributions in that material or in the Appropriate Legal Notices
displayed by works containing it; or
@item
Prohibiting misrepresentation of the origin of that material, or
requiring that modified versions of such material be marked in
reasonable ways as different from the original version; or
@item
Limiting the use for publicity purposes of names of licensors or
authors of the material; or
@item
Declining to grant rights under trademark law for use of some trade
names, trademarks, or service marks; or
@item
Requiring indemnification of licensors and authors of that material by
anyone who conveys the material (or modified versions of it) with
contractual assumptions of liability to the recipient, for any
liability that these contractual assumptions directly impose on those
licensors and authors.
@end enumerate
All other non-permissive additional terms are considered ``further
restrictions'' within the meaning of section 10. If the Program as you
received it, or any part of it, contains a notice stating that it is
governed by this License along with a term that is a further
restriction, you may remove that term. If a license document contains
a further restriction but permits relicensing or conveying under this
License, you may add to a covered work material governed by the terms
of that license document, provided that the further restriction does
not survive such relicensing or conveying.
If you add terms to a covered work in accord with this section, you
must place, in the relevant source files, a statement of the
additional terms that apply to those files, or a notice indicating
where to find the applicable terms.
Additional terms, permissive or non-permissive, may be stated in the
form of a separately written license, or stated as exceptions; the
above requirements apply either way.
@item Termination.
You may not propagate or modify a covered work except as expressly
provided under this License. Any attempt otherwise to propagate or
modify it is void, and will automatically terminate your rights under
this License (including any patent licenses granted under the third
paragraph of section 11).
However, if you cease all violation of this License, then your license
from a particular copyright holder is reinstated (a) provisionally,
unless and until the copyright holder explicitly and finally
terminates your license, and (b) permanently, if the copyright holder
fails to notify you of the violation by some reasonable means prior to
60 days after the cessation.
Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from that
copyright holder, and you cure the violation prior to 30 days after
your receipt of the notice.
Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
this License. If your rights have been terminated and not permanently
reinstated, you do not qualify to receive new licenses for the same
material under section 10.
@item Acceptance Not Required for Having Copies.
You are not required to accept this License in order to receive or run
a copy of the Program. Ancillary propagation of a covered work
occurring solely as a consequence of using peer-to-peer transmission
to receive a copy likewise does not require acceptance. However,
nothing other than this License grants you permission to propagate or
modify any covered work. These actions infringe copyright if you do
not accept this License. Therefore, by modifying or propagating a
covered work, you indicate your acceptance of this License to do so.
@item Automatic Licensing of Downstream Recipients.
Each time you convey a covered work, the recipient automatically
receives a license from the original licensors, to run, modify and
propagate that work, subject to this License. You are not responsible
for enforcing compliance by third parties with this License.
An ``entity transaction'' is a transaction transferring control of an
organization, or substantially all assets of one, or subdividing an
organization, or merging organizations. If propagation of a covered
work results from an entity transaction, each party to that
transaction who receives a copy of the work also receives whatever
licenses to the work the party's predecessor in interest had or could
give under the previous paragraph, plus a right to possession of the
Corresponding Source of the work from the predecessor in interest, if
the predecessor has it or can get it with reasonable efforts.
You may not impose any further restrictions on the exercise of the
rights granted or affirmed under this License. For example, you may
not impose a license fee, royalty, or other charge for exercise of
rights granted under this License, and you may not initiate litigation
(including a cross-claim or counterclaim in a lawsuit) alleging that
any patent claim is infringed by making, using, selling, offering for
sale, or importing the Program or any portion of it.
@item Patents.
A ``contributor'' is a copyright holder who authorizes use under this
License of the Program or a work on which the Program is based. The
work thus licensed is called the contributor's ``contributor version''.
A contributor's ``essential patent claims'' are all patent claims owned
or controlled by the contributor, whether already acquired or
hereafter acquired, that would be infringed by some manner, permitted
by this License, of making, using, or selling its contributor version,
but do not include claims that would be infringed only as a
consequence of further modification of the contributor version. For
purposes of this definition, ``control'' includes the right to grant
patent sublicenses in a manner consistent with the requirements of
this License.
Each contributor grants you a non-exclusive, worldwide, royalty-free
patent license under the contributor's essential patent claims, to
make, use, sell, offer for sale, import and otherwise run, modify and
propagate the contents of its contributor version.
In the following three paragraphs, a ``patent license'' is any express
agreement or commitment, however denominated, not to enforce a patent
(such as an express permission to practice a patent or covenant not to
sue for patent infringement). To ``grant'' such a patent license to a
party means to make such an agreement or commitment not to enforce a
patent against the party.
If you convey a covered work, knowingly relying on a patent license,
and the Corresponding Source of the work is not available for anyone
to copy, free of charge and under the terms of this License, through a
publicly available network server or other readily accessible means,
then you must either (1) cause the Corresponding Source to be so
available, or (2) arrange to deprive yourself of the benefit of the
patent license for this particular work, or (3) arrange, in a manner
consistent with the requirements of this License, to extend the patent
license to downstream recipients. ``Knowingly relying'' means you have
actual knowledge that, but for the patent license, your conveying the
covered work in a country, or your recipient's use of the covered work
in a country, would infringe one or more identifiable patents in that
country that you have reason to believe are valid.
If, pursuant to or in connection with a single transaction or
arrangement, you convey, or propagate by procuring conveyance of, a
covered work, and grant a patent license to some of the parties
receiving the covered work authorizing them to use, propagate, modify
or convey a specific copy of the covered work, then the patent license
you grant is automatically extended to all recipients of the covered
work and works based on it.
A patent license is ``discriminatory'' if it does not include within the
scope of its coverage, prohibits the exercise of, or is conditioned on
the non-exercise of one or more of the rights that are specifically
granted under this License. You may not convey a covered work if you
are a party to an arrangement with a third party that is in the
business of distributing software, under which you make payment to the
third party based on the extent of your activity of conveying the
work, and under which the third party grants, to any of the parties
who would receive the covered work from you, a discriminatory patent
license (a) in connection with copies of the covered work conveyed by
you (or copies made from those copies), or (b) primarily for and in
connection with specific products or compilations that contain the
covered work, unless you entered into that arrangement, or that patent
license was granted, prior to 28 March 2007.
Nothing in this License shall be construed as excluding or limiting
any implied license or other defenses to infringement that may
otherwise be available to you under applicable patent law.
@item No Surrender of Others' Freedom.
If conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License. If you cannot convey
a covered work so as to satisfy simultaneously your obligations under
this License and any other pertinent obligations, then as a
consequence you may not convey it at all. For example, if you agree
to terms that obligate you to collect a royalty for further conveying
from those to whom you convey the Program, the only way you could
satisfy both those terms and this License would be to refrain entirely
from conveying the Program.
@item Remote Network Interaction; Use with the GNU General Public License.
Notwithstanding any other provision of this License, if you modify the
Program, your modified version must prominently offer all users interacting
with it remotely through a computer network (if your version supports such
interaction) an opportunity to receive the Corresponding Source of your
version by providing access to the Corresponding Source from a network
server at no charge, through some standard or customary means of
facilitating copying of software. This Corresponding Source shall include
the Corresponding Source for any work covered by version 3 of the GNU
General Public License that is incorporated pursuant to the following
paragraph.
Notwithstanding any other provision of this License, you have permission to
link or combine any covered work with a work licensed under version 3 of
the GNU General Public License into a single combined work, and to convey
the resulting work. The terms of this License will continue to apply to
the part which is the covered work, but the work with which it is combined
will remain governed by version 3 of the GNU General Public License.
@item Revised Versions of this License.
The Free Software Foundation may publish revised and/or new versions
of the GNU Affero General Public License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns.
Each version is given a distinguishing version number. If the Program
specifies that a certain numbered version of the GNU Affero General Public
License ``or any later version'' applies to it, you have the option of
following the terms and conditions either of that numbered version or
of any later version published by the Free Software Foundation. If
the Program does not specify a version number of the GNU Affero General
Public License, you may choose any version ever published by the Free
Software Foundation.
If the Program specifies that a proxy can decide which future versions
of the GNU Affero General Public License can be used, that proxy's public
statement of acceptance of a version permanently authorizes you to
choose that version for the Program.
Later license versions may give you additional or different
permissions. However, no additional obligations are imposed on any
author or copyright holder as a result of your choosing to follow a
later version.
@item Disclaimer of Warranty.
THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM ``AS IS'' WITHOUT
WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND
PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE
DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR
CORRECTION.
@item Limitation of Liability.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR
CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES
ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT
NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR
LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM
TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER
PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
@item Interpretation of Sections 15 and 16.
If the disclaimer of warranty and limitation of liability provided
above cannot be given local legal effect according to their terms,
reviewing courts shall apply local law that most closely approximates
an absolute waiver of all civil liability in connection with the
Program, unless a warranty or assumption of liability accompanies a
copy of the Program in return for a fee.
@end enumerate
@heading END OF TERMS AND CONDITIONS
@heading How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these
terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least
the ``copyright'' line and a pointer to where the full notice is found.
@smallexample
@var{one line to give the program's name and a brief idea of what it does.}
Copyright (C) @var{year} @var{name of author}
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see @url{http://www.gnu.org/licenses/}.
@end smallexample
Also add information on how to contact you by electronic and paper mail.
If your software can interact with users remotely through a computer
network, you should also make sure that it provides a way for users to
get its source. For example, if your program is a web application, its
interface could display a ``Source'' link that leads users to an archive
of the code. There are many ways you could offer source, and different
solutions will be better for different programs; see section 13 for the
specific requirements.
You should also get your employer (if you work as a programmer) or school,
if any, to sign a ``copyright disclaimer'' for the program, if necessary.
For more information on this, and how to apply and follow the GNU AGPL, see
@url{http://www.gnu.org/licenses/}.

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*/
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padding: 0.5em;
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@c This file is used both in the exchange and merchant
@c manuals. Edits should be propagated to both Gits!
@node Configuration format
@section Configuration format
@cindex configuration
In Taler realm, any component obeys to the same pattern to get configuration
values. According to this pattern, once the component has been installed, the
installation deploys default values in @cite{$@{prefix@}/share/taler/config.d/}, in
@cite{.conf} files. In order to override these defaults, the user can write a custom
@cite{.conf} file and either pass it to the component at execution time, or name it
@cite{taler.conf} and place it under @cite{$HOME/.config/}.
A config file is a text file containing @cite{sections}, and each section contains
its @cite{values}. The right format follows:
@example
[section1]
value1 = string
value2 = 23
[section2]
value21 = string
value22 = /path22
@end example
Throughout any configuration file, it is possible to use @code{$}-prefixed variables,
like @code{$VAR}, especially when they represent filesystem paths.
It is also possible to provide defaults values for those variables that are unset,
by using the following syntax: @code{$@{VAR:-default@}}.
However, there are two ways a user can set @code{$}-prefixable variables:
by defining them under a @code{[paths]} section, see example below,
@example
[paths]
TALER_DEPLOYMENT_SHARED = $@{HOME@}/shared-data
..
[section-x]
path-x = $@{TALER_DEPLOYMENT_SHARED@}/x
@end example
or by setting them in the environment:
@example
$ export VAR=/x
@end example
The configuration loader will give precedence to variables set under @code{[path]},
though.
The utility @code{taler-config}, which gets installed along with the exchange, serves
to get and set configuration values without directly editing the @cite{.conf}.
The option @code{-f} is particularly useful to resolve pathnames, when they use
several levels of @code{$}-expanded variables. See @code{taler-config --help}.
Note that, in this stage of development, the file @code{$HOME/.config/taler.conf}
can contain sections for @emph{all} the component. For example, both an exchange and
a bank can read values from it.
The repository @code{git://taler.net/deployment} contains examples of configuration
file used in our demos. See under @code{deployment/config}.
@cartouche
@quotation Note
Expectably, some components will not work just by using default values, as their
work is often interdependent. For example, a merchant needs to know an exchange
URL, or a database name.
@end quotation
@end cartouche

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html, body {
font-size: 1em;
text-align: left;
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body {
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margin: 0 auto;
padding: .5em 1em 1em 1em;
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border-style: solid;
border-width: 3px;
}

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#!/bin/sh
taler-exchange-dbinit -r
java -jar schemaSpy_5.0.0.jar -t pgsql -db taler -o taler -host localhost -dp /usr/share/java/postgresql-jdbc3-9.2.jar -u grothoff -p test -s public -hq

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@c The GNU Free Documentation License.
@center Version 1.3, 3 November 2008
@c This file is intended to be included within another document,
@c hence no sectioning command or @node.
@display
Copyright @copyright{} 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
@uref{http://fsf.org/}
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
@end display
@enumerate 0
@item
PREAMBLE
The purpose of this License is to make a manual, textbook, or other
functional and useful document @dfn{free} in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible
for modifications made by others.
This License is a kind of ``copyleft'', which means that derivative
works of the document must themselves be free in the same sense. It
complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does. But this License is not limited to software manuals;
it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book. We recommend this License
principally for works whose purpose is instruction or reference.
@item
APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium, that
contains a notice placed by the copyright holder saying it can be
distributed under the terms of this License. Such a notice grants a
world-wide, royalty-free license, unlimited in duration, to use that
work under the conditions stated herein. The ``Document'', below,
refers to any such manual or work. Any member of the public is a
licensee, and is addressed as ``you''. You accept the license if you
copy, modify or distribute the work in a way requiring permission
under copyright law.
A ``Modified Version'' of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.
A ``Secondary Section'' is a named appendix or a front-matter section
of the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document's overall
subject (or to related matters) and contains nothing that could fall
directly within that overall subject. (Thus, if the Document is in
part a textbook of mathematics, a Secondary Section may not explain
any mathematics.) The relationship could be a matter of historical
connection with the subject or with related matters, or of legal,
commercial, philosophical, ethical or political position regarding
them.
The ``Invariant Sections'' are certain Secondary Sections whose titles
are designated, as being those of Invariant Sections, in the notice
that says that the Document is released under this License. If a
section does not fit the above definition of Secondary then it is not
allowed to be designated as Invariant. The Document may contain zero
Invariant Sections. If the Document does not identify any Invariant
Sections then there are none.
The ``Cover Texts'' are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that
the Document is released under this License. A Front-Cover Text may
be at most 5 words, and a Back-Cover Text may be at most 25 words.
A ``Transparent'' copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, that is suitable for revising the document
straightforwardly with generic text editors or (for images composed of
pixels) generic paint programs or (for drawings) some widely available
drawing editor, and that is suitable for input to text formatters or
for automatic translation to a variety of formats suitable for input
to text formatters. A copy made in an otherwise Transparent file
format whose markup, or absence of markup, has been arranged to thwart
or discourage subsequent modification by readers is not Transparent.
An image format is not Transparent if used for any substantial amount
of text. A copy that is not ``Transparent'' is called ``Opaque''.
Examples of suitable formats for Transparent copies include plain
@sc{ascii} without markup, Texinfo input format, La@TeX{} input
format, @acronym{SGML} or @acronym{XML} using a publicly available
@acronym{DTD}, and standard-conforming simple @acronym{HTML},
PostScript or @acronym{PDF} designed for human modification. Examples
of transparent image formats include @acronym{PNG}, @acronym{XCF} and
@acronym{JPG}. Opaque formats include proprietary formats that can be
read and edited only by proprietary word processors, @acronym{SGML} or
@acronym{XML} for which the @acronym{DTD} and/or processing tools are
not generally available, and the machine-generated @acronym{HTML},
PostScript or @acronym{PDF} produced by some word processors for
output purposes only.
The ``Title Page'' means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the material
this License requires to appear in the title page. For works in
formats which do not have any title page as such, ``Title Page'' means
the text near the most prominent appearance of the work's title,
preceding the beginning of the body of the text.
The ``publisher'' means any person or entity that distributes copies
of the Document to the public.
A section ``Entitled XYZ'' means a named subunit of the Document whose
title either is precisely XYZ or contains XYZ in parentheses following
text that translates XYZ in another language. (Here XYZ stands for a
specific section name mentioned below, such as ``Acknowledgements'',
``Dedications'', ``Endorsements'', or ``History''.) To ``Preserve the Title''
of such a section when you modify the Document means that it remains a
section ``Entitled XYZ'' according to this definition.
The Document may include Warranty Disclaimers next to the notice which
states that this License applies to the Document. These Warranty
Disclaimers are considered to be included by reference in this
License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and has
no effect on the meaning of this License.
@item
VERBATIM COPYING
You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies
to the Document are reproduced in all copies, and that you add no other
conditions whatsoever to those of this License. You may not use
technical measures to obstruct or control the reading or further
copying of the copies you make or distribute. However, you may accept
compensation in exchange for copies. If you distribute a large enough
number of copies you must also follow the conditions in section 3.
You may also lend copies, under the same conditions stated above, and
you may publicly display copies.
@item
COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly have
printed covers) of the Document, numbering more than 100, and the
Document's license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover
Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover. Both covers must also clearly and legibly identify
you as the publisher of these copies. The front cover must present
the full title with all words of the title equally prominent and
visible. You may add other material on the covers in addition.
Copying with changes limited to the covers, as long as they preserve
the title of the Document and satisfy these conditions, can be treated
as verbatim copying in other respects.
If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.
If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy
a computer-network location from which the general network-using
public has access to download using public-standard network protocols
a complete Transparent copy of the Document, free of added material.
If you use the latter option, you must take reasonably prudent steps,
when you begin distribution of Opaque copies in quantity, to ensure
that this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you distribute an
Opaque copy (directly or through your agents or retailers) of that
edition to the public.
It is requested, but not required, that you contact the authors of the
Document well before redistributing any large number of copies, to give
them a chance to provide you with an updated version of the Document.
@item
MODIFICATIONS
You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release
the Modified Version under precisely this License, with the Modified
Version filling the role of the Document, thus licensing distribution
and modification of the Modified Version to whoever possesses a copy
of it. In addition, you must do these things in the Modified Version:
@enumerate A
@item
Use in the Title Page (and on the covers, if any) a title distinct
from that of the Document, and from those of previous versions
(which should, if there were any, be listed in the History section
of the Document). You may use the same title as a previous version
if the original publisher of that version gives permission.
@item
List on the Title Page, as authors, one or more persons or entities
responsible for authorship of the modifications in the Modified
Version, together with at least five of the principal authors of the
Document (all of its principal authors, if it has fewer than five),
unless they release you from this requirement.
@item
State on the Title page the name of the publisher of the
Modified Version, as the publisher.
@item
Preserve all the copyright notices of the Document.
@item
Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.
@item
Include, immediately after the copyright notices, a license notice
giving the public permission to use the Modified Version under the
terms of this License, in the form shown in the Addendum below.
@item
Preserve in that license notice the full lists of Invariant Sections
and required Cover Texts given in the Document's license notice.
@item
Include an unaltered copy of this License.
@item
Preserve the section Entitled ``History'', Preserve its Title, and add
to it an item stating at least the title, year, new authors, and
publisher of the Modified Version as given on the Title Page. If
there is no section Entitled ``History'' in the Document, create one
stating the title, year, authors, and publisher of the Document as
given on its Title Page, then add an item describing the Modified
Version as stated in the previous sentence.
@item
Preserve the network location, if any, given in the Document for
public access to a Transparent copy of the Document, and likewise
the network locations given in the Document for previous versions
it was based on. These may be placed in the ``History'' section.
You may omit a network location for a work that was published at
least four years before the Document itself, or if the original
publisher of the version it refers to gives permission.
@item
For any section Entitled ``Acknowledgements'' or ``Dedications'', Preserve
the Title of the section, and preserve in the section all the
substance and tone of each of the contributor acknowledgements and/or
dedications given therein.
@item
Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers
or the equivalent are not considered part of the section titles.
@item
Delete any section Entitled ``Endorsements''. Such a section
may not be included in the Modified Version.
@item
Do not retitle any existing section to be Entitled ``Endorsements'' or
to conflict in title with any Invariant Section.
@item
Preserve any Warranty Disclaimers.
@end enumerate
If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant. To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.
You may add a section Entitled ``Endorsements'', provided it contains
nothing but endorsements of your Modified Version by various
parties---for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.
You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version. Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity. If the Document already
includes a cover text for the same cover, previously added by you or
by arrangement made by the same entity you are acting on behalf of,
you may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.
@item
COMBINING DOCUMENTS
You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice, and that you preserve all their Warranty Disclaimers.
The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.
In the combination, you must combine any sections Entitled ``History''
in the various original documents, forming one section Entitled
``History''; likewise combine any sections Entitled ``Acknowledgements'',
and any sections Entitled ``Dedications''. You must delete all
sections Entitled ``Endorsements.''
@item
COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this
License in the various documents with a single copy that is included in
the collection, provided that you follow the rules of this License for
verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and distribute
it individually under this License, provided you insert a copy of this
License into the extracted document, and follow this License in all
other respects regarding verbatim copying of that document.
@item
AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an ``aggregate'' if the copyright
resulting from the compilation is not used to limit the legal rights
of the compilation's users beyond what the individual works permit.
When the Document is included in an aggregate, this License does not
apply to the other works in the aggregate which are not themselves
derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document's Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.
@item
TRANSLATION
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers. In case of a disagreement between
the translation and the original version of this License or a notice
or disclaimer, the original version will prevail.
If a section in the Document is Entitled ``Acknowledgements'',
``Dedications'', or ``History'', the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual
title.
@item
TERMINATION
You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License. Any attempt
otherwise to copy, modify, sublicense, or distribute it is void, and
will automatically terminate your rights under this License.
However, if you cease all violation of this License, then your license
from a particular copyright holder is reinstated (a) provisionally,
unless and until the copyright holder explicitly and finally
terminates your license, and (b) permanently, if the copyright holder
fails to notify you of the violation by some reasonable means prior to
60 days after the cessation.
Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from that
copyright holder, and you cure the violation prior to 30 days after
your receipt of the notice.
Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
this License. If your rights have been terminated and not permanently
reinstated, receipt of a copy of some or all of the same material does
not give you any rights to use it.
@item
FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions
of the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
@uref{http://www.gnu.org/copyleft/}.
Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License ``or any later version'' applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation. If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation. If the Document
specifies that a proxy can decide which future versions of this
License can be used, that proxy's public statement of acceptance of a
version permanently authorizes you to choose that version for the
Document.
@item
RELICENSING
``Massive Multiauthor Collaboration Site'' (or ``MMC Site'') means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works. A
public wiki that anybody can edit is an example of such a server. A
``Massive Multiauthor Collaboration'' (or ``MMC'') contained in the
site means any set of copyrightable works thus published on the MMC
site.
``CC-BY-SA'' means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.
``Incorporate'' means to publish or republish a Document, in whole or
in part, as part of another Document.
An MMC is ``eligible for relicensing'' if it is licensed under this
License, and if all works that were first published under this License
somewhere other than this MMC, and subsequently incorporated in whole
or in part into the MMC, (1) had no cover texts or invariant sections,
and (2) were thus incorporated prior to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the site
under CC-BY-SA on the same site at any time before August 1, 2009,
provided the MMC is eligible for relicensing.
@end enumerate
@page
@heading ADDENDUM: How to use this License for your documents
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:
@smallexample
@group
Copyright (C) @var{year} @var{your name}.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
@end group
@end smallexample
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the ``with@dots{}Texts.'' line with this:
@smallexample
@group
with the Invariant Sections being @var{list their titles}, with
the Front-Cover Texts being @var{list}, and with the Back-Cover Texts
being @var{list}.
@end group
@end smallexample
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.
@c Local Variables:
@c ispell-local-pdict: "ispell-dict"
@c End:

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@c Syntax highlighting for texinfo's HTML output
@html
<script src="highlight.pack.js"></script>
<script>
var hls = [];
var syntaxAuto = true;
addEventListener("DOMContentLoaded", function() {
// Highlight blocks with fixed language
for (let x of hls) {
let next = x[0].nextElementSibling;
console.log("next", next);
let blocks = next.querySelectorAll("pre.example");
for (let i = 0; i < blocks.length; i++) {
blocks[i].classList.add("language-" + x[1]);
hljs.highlightBlock(blocks[i]);
}
}
// auto-detect other blocks if not disabled
if (syntaxAuto) {
let blocks = document.querySelectorAll("pre.example");
for (let i = 0; i < blocks.length; i++) {
hljs.highlightBlock(blocks[i]);
}
}
});
</script>
@end html
@macro setsyntax{lang}
@html
<script>
hls.push([document.currentScript, "\lang\"]);
</script>
@end html
@end macro
@macro setsyntaxnoauto{}
@html
<script>
syntaxAuto = false;
</script>
@end html
@end macro

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@ -1,47 +0,0 @@
@c This file is used both in the exchange and merchant
@c manuals. Edits should be propagated to both Gits!
@node Using taler-config
@section Using taler-config
@cindex taler-config
The tool @code{taler-config} can be used to
extract or manipulate configuration values; however, the configuration
use the well-known INI file format and can also be edited by hand.
Run
@example
$ taler-config -s $SECTION
@end example
to list all of the configuration values in section @code{$SECTION}.
Run
@example
$ taler-config -s $section -o $option
@end example
to extract the respective configuration value for option @code{$option}
in section @code{$section}.
Finally, to change a setting, run
@example
$ taler-config -s $section -o $option -V $value
@end example
to set the respective configuration value to @code{$value}. Note that you have to
manually restart the Taler backend after you change the configuration to
make the new configuration go into effect.
Some default options will use $-variables, such as @code{$DATADIR}
within their value. To expand the @code{$DATADIR} or other $-variables
in the configuration, pass the @code{-f} option to
@code{taler-config}. For example, compare:
@example
$ taler-config -s ACCOUNT-bank \
-o WIRE_RESPONSE
$ taler-config -f -s ACCOUNT-bank \
-o WIRE_RESPONSE
@end example
While the configuration file is typically located at
@code{$HOME/.config/taler.conf}, an alternative location can be
specified to @code{taler-merchant-httpd} and @code{taler-config} using
the @code{-c} option.

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@ -1,972 +0,0 @@
\input texinfo @c -*-texinfo-*-
@setfilename taler-exchange.info
@documentencoding UTF-8
@include version.texi
@settitle The GNU Taler Exchange Operator Manual
@paragraphindent 0
@exampleindent 4
@include syntax.texi
@copying
This manual is for the GNU Taler Exchange
(version @value{VERSION}, @value{UPDATED}),
a payment service provider for GNU Taler.
Copyright @copyright{} 2014-2018 Taler Systems SA
@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled "GNU
Free Documentation License".
@end quotation
@end copying
@dircategory Network applications
@direntry
* GNU Taler Exchange: (taler-exchange). Electronic payment system.
@end direntry
@titlepage
@title The GNU Taler Exchange Operator Manual
@subtitle Version @value{VERSION}
@subtitle @value{UPDATED}
@author Christian Grothoff (@email{grothoff@@taler.net})
@author Marcello Stanisci (@email{stanisci@@taler.net})
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage
@summarycontents
@contents
@ifnottex
@node Top
@top The GNU Taler Exchange Operator Manual
@insertcopying
@end ifnottex
@menu
* Introduction::
* Installation::
* Configuration::
* Deployment::
* Diagnostics::
Appendices
* GNU-AGPL:: The GNU Affero General Public License says how you
can copy and share the code of the `GNU Taler Exchange'.
* GNU-FDL:: The GNU Free Documentation License says how you
can copy and share the documentation of `GNU Taler'.
Indices
* Concept Index:: Index of concepts and programs.
@end menu
@node Introduction
@chapter Introduction
This manual is an early draft that still needs significant editing
work to become readable.
@section About GNU Taler
GNU Taler is an open protocol for an electronic payment system with a
free software reference implementation. GNU Taler offers secure, fast
and easy payment processing using well understood cryptographic
techniques. GNU Taler allows customers to remain anonymous, while
ensuring that merchants can be held accountable by governments.
Hence, GNU Taler is compatible with anti-money-laundering (AML) and
know-your-customer (KYC) regulation, as well as data protection
regulation (such as GDPR).
GNU Taler is not yet production-ready, after following this manual
you will have a backend that can process payments in ``KUDOS'', but
not regular currencies. This is not so much because of limitations
in the backend, but because we are not aware of a Taler exchange
operator offering regular currencies today.
@section About this manual
This tutorial targets system administrators who want to install and
operate a GNU Taler exchange.
@section Organizational prerequisites
Operating a GNU Taler exchange means that you are operating a payment
service provider, which means that you will most likely need a bank
license and/or follow applicable financial regulation.
@cindex availability
@cindex backup
@cindex replication
GNU Taler payment service providers generally need to ensure high
availability and have @emph{really} good backups (synchronous
replication, asynchronous remote replication, off-site backup, 24/7
monitoring, etc.).@footnote{Naturally, you could operate a Taler
exchange for a toy currency without any real value on low-cost setups
like a Raspberry Pi, but we urge you to limit the use of such setups
to research and education as with GNU Taler data loss instantly
results in financial losses.} This manual will not cover these
aspects of operating a payment service provider.
@cindex HSM
@cindex offline
@cindex database
@cindex operational security
We will assume that you can operate a (high-availability,
high-assurance) Postgres database. Furthermore, we expect some
moderate familiarity with the compilation and installation of free
software packages. You need to understand the cryptographic concepts
of private and public keys and must be able to protect private keys
stored in files on disk. An exchange uses an @emph{offline} master
key as well as @emph{online} keys. You are advised to secure your
private master key and any copies on encrypted, always-offline
computers. Again, we assume that you are familiar with good best
practices in operational security, including securing key
material.@footnote{The current implementation does not make provisions
for secret splitting. Still, the use of a hardware security module
(HSM) for protecting private keys is adviseable, so please contact the
developers for HSM integration support.}
@section Architecture overview
@cindex crypto-currency
@cindex bank
@cindex escrow
@cindex coin
Taler is a pure payment system, not a new crypto-currency. As such, it
operates in a traditional banking context. In particular, this means
that in order to receive funds via Taler, the merchant must have a
regular bank account, and payments can be executed in ordinary
currencies such as USD or EUR. Similarly, the Taler exchange must
interact with a bank. The bank of the exchange holds the exchange's
funds in an escrow account.
@cindex reserve
@cindex fee
@cindex aggregator
@cindex deposit
When customers wire money to the escrow account, the bank notifies
the exchange about the incoming wire transfers. The exchange then
creates a @emph{reserve} based on the subject of the wire transfer.
The wallet which knows the secret key matching the wire transfer
subject can then withdraw coins from the reserve, thereby draining
it. The liability of the exchange against the reserve is thereby
converted into a liability against digital coins issued by the
exchange. When the customer later spends the coins at a merchant,
and the merchant @emph{deposits} the coins at the exchange, the
exchange first @emph{aggregates} the amount from multiple deposits
from the same merchant and then instructs its bank to make a
wire transfer to the merchant, thereby fulfilling its obligation
and eliminating the liability. The exchange charges @emph{fees}
for some or all of its operations to cover costs and possibly make
a profit.
@cindex auditor
@cindex accounting
@emph{Auditors} are third parties, for example financial regulators,
that verify that the exchange operates correctly. The same software
is also used to calculate the exchange's profits, risk and liabilities
by the accountants of the exchange.
The Taler software stack for an exchange consists of the
following components:
@itemize
@cindex HTTP frontend
@item The HTTP frontend interacts with Taler wallets and
merchant backends. It is used to withdraw coins, deposit
coins, refresh coins, issue refunds, map wire transfers to
Taler transactions, inquire about the exchange's bank account
details, signing keys and fee structure.
The binary is the @code{taler-exchange-httpd}.
@cindex Aggregator
@item The aggregator combines multiple deposits made by
the same merchant and (eventually) triggers wire transfers for the
aggregate amount. The merchant can control how quickly wire
transfers are made. The exchange may be charge a fee per wire transfer
to discourage excessively frequent transfers. The binary
is the @code{taler-exchange-aggregator}.
@cindex Auditor
@item The auditor verifies that the transactions performed by
the exchange were done properly. It checks the various signatures,
totals up the amounts and alerts the operator to any inconsistencies.
It also computes the expected bank balance, revenue and risk exposure
of the exchange operator. The main binary is the
@code{taler-auditor}.
@cindex Wire plugin
@item A wire plugin enables the HTTP frontend to talk to the
bank. Its role is to allow the exchange to validate bank
addresses (i.e. IBAN numbers), for the aggregator to execute
wire transfers and for the auditor to query bank transaction
histories. Wire plugins are @emph{plugins} as there can be
many different implementations to deal with different
banking standards. Wire plugins are automatically located
and used by the exchange, aggregator and auditor.
@cindex DBMS
@cindex Postgres
@item The exchange requires a DBMS to stores the transaction history for
the Taler exchange and aggregator, and a (typically separate) DBMS for
the Taler auditor.
For now, the GNU Taler reference implemenation only supports Postgres,
but the code could be easily extended to support another DBMS.
@end itemize
@c The following image illustrates the various interactions of these
@c key components:
@c @center @image{arch, 3in, 4in}
@node Installation
@chapter Installation
Please install the following packages before proceeding with the exchange compilation.
@itemize
@item
GNU autoconf >= 2.69
@item
GNU automake >= 1.14
@item
GNU libtool >= 2.4
@item
GNU autopoint >= 0.19
@item
GNU libltdl >= 2.4
@item
GNU libunistring >= 0.9.3
@item
libcurl >= 7.26 (or libgnurl >= 7.26)
@item
GNU libmicrohttpd >= 0.9.59
@item
GNU libgcrypt >= 1.6
@item
libjansson >= 2.7
@item
Postgres >= 9.6, including libpq
@item
libgnunetutil (from Git)
@item
GNU Taler exchange (from Git)
@end itemize
Except for the last two, these are available in most GNU/Linux
distributions and should just be installed using the respective
package manager.
The following instructions will show how to install libgnunetutil and
the GNU Taler exchange.
Before you install libgnunetutil, you must download and install the
dependencies mentioned above, otherwise the build may succeed but fail
to export some of the tooling required by Taler.
To download and install libgnunetutil, proceed as follows:
@example
$ git clone https://git.gnunet.org/gnunet/
$ cd gnunet/
$ ./bootstrap
$ ./configure [--prefix=GNUNETPFX]
$ # Each dependency can be fetched from non standard locations via
$ # the '--with-<LIBNAME>' option. See './configure --help'.
$ make
# make install
@end example
If you did not specify a prefix, GNUnet will install to
@code{/usr/local}, which requires you to run the last step as
@code{root}.
To download and install the GNU Taler exchange, proceeds as follows:
@setsyntax shell
@example
$ git clone git://git.taler.net/exchange
$ cd exchange
$ ./bootstrap
$ ./configure [--prefix=EXCHANGEPFX] \
[--with-gnunet=GNUNETPFX]
$ # Each dependency can be fetched from non standard locations via
$ # the '--with-<LIBNAME>' option. See './configure --help'.
$ make
# make install
@end example
If you did not specify a prefix, the exchange will install to
@code{/usr/local}, which requires you to run the last step as
@code{root}. Note that you have to specify @code{--with-gnunet=/usr/local}
if you installed GNUnet to @code{/usr/local} in the previous step.
@node Configuration
@chapter Configuration
@c In this document, we assume that @code{$HOME/.config/taler.conf} is being customized.
This chapter provides an overview of the exchange configuration. Or
at least eventually will do so, for now it is a somewhat wild
description of some of the options.
@menu
* Configuration format::
* Using taler-config::
* Keying::
* Serving::
* Currency::
* Bank account::
* Database::
* Coins (denomination keys): Coins denomination keys.
* Keys duration::
@end menu
@include configuration-format.texi
@include taler-config.texi
@node Keying
@section Keying
The exchange works with three types of keys:
@c FIXME: explain better!
@itemize
@item
@cite{master key}
@item
@cite{sign keys}
@item
@cite{denomination keys} (see section @cite{Coins})
@end itemize
@c FIXME: text here.
@itemize
@item
@cite{MASTER_PRIV_FILE}: Path to the exchange's master private file.
@item
@cite{MASTER_PUBLIC_KEY}: Must specify the exchange's master public key.
@end itemize
@node Serving
@section Serving
The exchange can serve HTTP over both TCP and UNIX domain socket.
The following values are to be configured in the section
@cite{[exchange]}:
@itemize
@item
@cite{serve}: must be set to @cite{tcp} to serve HTTP over TCP, or
@cite{unix} to serve HTTP over a UNIX domain socket
@item
@cite{port}: Set to the TCP port to listen on if @cite{serve} Is
@cite{tcp}.
@item
@cite{unixpath}: set to the UNIX domain socket path to listen on if
@cite{serve} Is @cite{unix}
@item
@cite{unixpath_mode}: number giving the mode with the access
permission MASK for the @cite{unixpath} (i.e. 660 = rw-rw----).
@end itemize
@node Currency
@section Currency
The exchange supports only one currency. This data is set under the respective
option @cite{currency} in section @cite{[taler]}.
@node Bank account
@section Bank account
To configure a bank account in Taler, we need to furnish four
pieces of information:
@itemize
@item
The @code{payto://} URL of the bank account, which uniquely idenfies
the account. Examples for such URLs include
@code{payto://sepa/CH9300762011623852957} for a bank account
in the single European payment area (SEPA) or
@code{payto://x-taler-bank/localhost:8080/2} for the 2nd bank
account a the Taler bank demonstrator running at @code{localhost}
on port 8080. The first part of the URL following @code{payto://}
(``sepa'' or ``x-taler-bank'') is called the wire method.
@item
A matching wire plugin that implements a protocol to interact
with the banking system. For example, the EBICS plugin can
be used for SEPA transfers, or the ``taler-bank'' plugin can
interact with the Taler bank demonstrator. A wire plugin
only supports one particular wire method. Thus, you must make
sure to pick a plugin that supports the wire method used in the
URL.
@item
A file containing the signed JSON-encoded bank account details
for the /wire API. This is necessary as Taler supports offline
signing for bank accounts for additional security.
@item
Finally, the plugin needs to be provided resources for
authentication to the respective banking service. The format
in which the authentication information must be provided
depends on the wire plugin.
@end itemize
You can configure multiple accounts for an exchange by creating
sections starting with ``account-'' for the section name. You can
ENABLE for each account whether it should be used, and for what
(incoming or outgoing wire transfers):
@setsyntax ini
@example
[account-1]
URL = "payto://sepa/CH9300762011623852957"
WIRE_RESPONSE = $@{TALER_CONFIG_HOME@}/account-1.json
# Currently, only the 'taler_bank' plugin is implemented.
PLUGIN = <plugin_name_here>
# Use for exchange-aggregator (outgoing transfers)
ENABLE_DEBIT = YES
# Use for exchange-wirewatch (and listed in /wire)
ENABLE_CREDIT = YES
# Authentication options for the chosen plugin go here.
# (Next sections have examples of authentication mechanisms)
@end example
The command line tool @cite{taler-exchange-wire} is used to create
the @code{account-1.json} file.
For example, the utility may be invoked as follows to create
all of the WIRE_RESPONSE files (in the locations specified by the configuration):
@example
$ taler-exchange-wire
@end example
The generated file will be echoed by the exchange when serving
/wire@footnote{https://api.taler.net/api-exchange.html#wire-req}
requests.
@menu
* Wire plugin ``taler_bank''::
* Wire plugin ``ebics''::
* Wire fee structure::
@end menu
@node Wire plugin ``taler_bank''
@subsection Wire plugin ``taler_bank''
@cindex x-taler-bank
@cindex taler_bank plugin
The @code{taler_bank} plugin implements the wire method ``x-taler-bank''.
The format of the @code{payto://} URL is @code{payto://x-taler-bank/HOSTNAME[:PORT]}.
For basic authentication, the @code{taler_bank} plugin only supports
simple password-based authentication. For this, the configuration
must contain the ``USERNAME'' and ``PASSWORD'' of the respective
account at the bank.
@setsyntax ini
@example
[account-1]
# Bank account details here..
# ..
# Authentication options for the taler_bank plugin below:
TALER_BANK_AUTH_METHOD = basic
USERNAME = exchange
PASSWORD = super-secure
@end example
@node Wire plugin ``ebics''
@subsection Wire plugin ``ebics''
The ``ebics'' wire plugin is not fully implemented and today
does not support actual wire transfers.
@cartouche
@quotation Note
The rationale behind having multiple bank accounts is that the exchange operator, as a security
measure, may want to instruct the bank that the incoming bank account is only supposed to
@emph{receive} money.
@end quotation
@end cartouche
@node Wire fee structure
@subsection Wire fee structure
@cindex wire fee
@cindex fee
For each wire method (``sepa'' or ``x-taler-wire'', but not per plugin!) the
exchange configuration must specify applicable wire fees. This is done
in configuration sections of the format @code{fees-METHOD}. There are two
types of fees, simple wire fees and closing fees. Wire fees apply whenever
the aggregator transfers funds to a merchant. Closing fees apply whenever
the exchange closes a reserve (sending back funds to the customer). The
fees must be constant for a full year, which is specified as part of the name
of the option.
@setsyntax ini
@example
[fees-iban]
WIRE-FEE-2018 = EUR:0.01
WIRE-FEE-2019 = EUR:0.01
CLOSING-FEE-2018 = EUR:0.01
CLOSING-FEE-2019 = EUR:0.01
[fees-x-taler-bank]
WIRE-FEE-2018 = KUDOS:0.01
WIRE-FEE-2019 = KUDOS:0.01
CLOSING-FEE-2018 = KUDOS:0.01
CLOSING-FEE-2019 = KUDOS:0.01
@end example
@node Database
@section Database
The option @cite{db} under section @cite{[exchange]} gets the DB backend's name the exchange
is going to use. So far, only @cite{db = postgres} is supported. After choosing the backend,
it is mandatory to supply the connection string (namely, the database name). This is
possible in two ways:
@itemize
@item
via an environment variable: @cite{TALER_EXCHANGEDB_POSTGRES_CONFIG}.
@item
via configuration option @cite{CONFIG}, under section @cite{[exchangedb-BACKEND]}. For example, the demo exchange is configured as follows:
@end itemize
@setsyntax ini
@example
[exchange]
...
DB = postgres
...
[exchangedb-postgres]
CONFIG = postgres:///talerdemo
@end example
@node Coins denomination keys
@section Coins (denomination keys)
Sections specifying denomination (coin) information start with
"coin_". By convention, the name continues with
"$CURRENCY_[$SUBUNIT]_$VALUE", i.e. @cite{[coin_eur_ct_10]} for a 10
cent piece. However, only the "coin_" prefix is mandatory. Each
"coin_"-section must then have the following options:
@itemize
@item
@cite{value}: How much is the coin worth, the format is
CURRENCY:VALUE.FRACTION. For example, a 10 cent piece is "EUR:0.10".
@item
@cite{duration_withdraw}: How long can a coin of this type be
withdrawn? This limits the losses incurred by the exchange when a
denomination key is compromised.
@item
@cite{duration_overlap}: What is the overlap of the withdrawal
timespan for this coin type?
@item
@cite{duration_spend}: How long is a coin of the given type valid?
Smaller values result in lower storage costs for the exchange.
@item
@cite{fee_withdraw}: What does it cost to withdraw this coin?
Specified using the same format as @cite{value}.
@item
@cite{fee_deposit}: What does it cost to deposit this coin? Specified
using the same format as @cite{value}.
@item
@cite{fee_refresh}: What does it cost to refresh this coin? Specified
using the same format as @cite{value}.
@item
@cite{rsa_keysize}: How many bits should the RSA modulus (product of
the two primes) have for this type of coin.
@end itemize
@node Keys duration
@section Keys duration
Both @cite{signkeys} and @cite{denom keys} have a starting date. The
option @cite{lookahead_provide}, under section @cite{[exchange]},
is such that only keys whose starting date is younger than
@cite{lookahead_provide} will be issued by the exchange.
@cite{signkeys}. The option @cite{lookahead_sign} is such that, being
@cite{t} the time when @cite{taler-exchange-keyup} is run,
@cite{taler-exchange-keyup} will generate @cite{n} @cite{signkeys},
where @cite{t + (n * signkey_duration) = t + lookahead_sign}. In other
words, we generate a number of keys which is sufficient to cover a
period of @cite{lookahead_sign}. As for the starting date, the first
generated key will get a starting time of @cite{t}, and the
@cite{j}-th key will get a starting time of @cite{x +
signkey_duration}, where @cite{x} is the starting time of the
@cite{(j-1)}-th key.
@cite{denom keys}. The option @cite{lookahead_sign} is such that,
being @cite{t} the time when @cite{taler-exchange-keyup} is run,
@cite{taler-exchange-keyup} will generate @cite{n} @cite{denom keys}
for each denomination, where @cite{t + (n * duration_withdraw) = t +
lookahead_sign}. In other words, for each denomination, we generate a
number of keys which is sufficient to cover a period of
@cite{lookahead_sign}. As for the starting date, the first generated
key will get a starting time of @cite{t}, and the @cite{j}-th key will
get a starting time of @cite{x + duration_withdraw}, where @cite{x} is
the starting time of the @cite{(j-1)}-th key.
To change these settings, edit the following
values in section @cite{[exchange]}:
@itemize
@item
@cite{SIGNKEY_DURATION}: How long should one signing key be used?
@item
@cite{LOOKAHEAD_SIGN}: How much time we want to cover with our
signing keys? Note that if @cite{SIGNKEY_DURATION} is bigger than
@cite{LOOKAHEAD_SIGN}, @code{taler-exchange-keyup} will generate a
quantity of signing keys which is sufficient to cover all the
gap.
@end itemize
@c FIXME: LEGAL_DURATION not covered!
@c FIXME: LOOKAHEAD_PROVIDE not covered!
@node Deployment
@chapter Deployment
@menu
* Keys generation::
* Database upgrades::
@end menu
@node Keys generation
@section Keys generation
Once the configuration is properly set up, all the keys can be generated
by the tool @code{taler-exchange-keyup}. The following command generates denomkeys
and signkeys, plus the "blob" that is to be signed by the auditor.
@example
taler-exchange-keyup -o blob
@end example
@emph{blob} contains data about denomkeys that the exchange operator needs to
get signed by every auditor he wishes (or is forced to) work with.
In a normal scenario, an auditor must have some way of receiving the blob to
sign (Website, manual delivery, ..). Nonetheless, the exchange admin can fake
an auditor signature --- for testing purposes --- by running the following command
@example
taler-auditor-sign -m EXCHANGE_MASTER_PUB -r BLOB -u AUDITOR_URL -o OUTPUT_FILE
@end example
Those arguments are all mandatory.
@itemize
@item @code{EXCHANGE_MASTER_PUB} the base32 Crockford-encoded exchange's master
public key. Tipically, this value lies in the configuration option
@code{[exchange]/master_public_key}.
@item @code{BLOB} the blob generated in the previous step.
@item @code{AUDITOR_URL} the URL that identifies the auditor.
@item @code{OUTPUT_FILE} where on the disk the signed blob is to be saved.
@end itemize
@code{OUTPUT_FILE} must then be copied into the directory specified
by the option @code{AUDITOR_BASE_DIR} under the section @code{[exchangedb]}.
Assuming @code{AUDITOR_BASE_DIR = $@{HOME@}/.local/share/taler/auditors}, the
following command will "add" the auditor identified by @code{AUDITOR_URL} to
the exchange.
@example
cp OUTPUT_FILE $@{HOME@}/.local/share/taler/auditors
@end example
If the auditor has been correctly added, the exchange's @code{/keys} response
must contain an entry in the @code{auditors} array mentioning the auditor's URL.
@c FIXME: reference section about where keys are stored.
@node Database upgrades
@section Database upgrades
Currently, there is no way to upgrade the database between Taler versions.
The exchange database can be re-initialized using:
@example
$ taler-exchange-dbinit -r
@end example
However, running this command will result in all data in the database
being lost, which may result in significant financial liabilities as
the exchange can then not detect double-spending. Hence this
operation must not be performed in a production system.
@node Diagnostics
@chapter Diagnostics
This chapter includes various (very unpolished) sections on specific topics
that might be helpful to understand how the exchange operates, which files
should be backed up. The information may also be helpful for diagnostics.
@menu
* Reserve management::
* Database Scheme::
* Signing key storage::
* Denomination key storage::
* Auditor signature storage::
@end menu
@node Reserve management
@section Reserve management
Incoming transactions to the exchange's provider result in the
creation or update of reserves, identified by their reserve key. The
command line tool @cite{taler-exchange-reservemod} allows create and
add money to reserves in the exchange's database.
@node Database Scheme
@section Database Scheme
The exchange database must be initialized using @cite{taler-exchange-dbinit}. This
tool creates the tables required by the Taler exchange to operate. The
tool also allows you to reset the Taler exchange database, which is useful
for test cases but should never be used in production. Finally,
@cite{taler-exchange-dbinit} has a function to garbage collect a database,
allowing administrators to purge records that are no longer required.
The database scheme used by the exchange look as follows:
@image{exchange-db,5in,,,png}
@node Signing key storage
@section Signing key storage
The private online signing keys of the exchange are stored in a
subdirectory "signkeys/" of the "KEYDIR" which is an option in the
"[exchange]" section of the configuration file. The filename is the
starting time at which the signing key can be used in microseconds
since the Epoch. The file format is defined by the @cite{struct TALER_EXCHANGEDB_PrivateSigningKeyInformationP}:
@example
struct TALER_EXCHANGEDB_PrivateSigningKeyInformationP @{
struct TALER_ExchangePrivateKeyP signkey_priv;
struct TALER_ExchangeSigningKeyValidityPS issue;
@};
@end example
@node Denomination key storage
@section Denomination key storage
The private denomination keys of the exchange are store in a
subdirectory "denomkeys/" of the "KEYDIR" which is an option in the
"[exchange]" section of the configuration file. "denomkeys/" contains
further subdirectories, one per denomination. The specific name of
the subdirectory under "denomkeys/" is ignored by the exchange.
However, the name is important for the "taler-exchange-keyup" tool
that generates the keys. The tool combines a human-readable encoding
of the denomination (i.e. for EUR:1.50 the prefix would be
"EUR_1_5-", or for EUR:0.01 the name would be "EUR_0_01-") with a
postfix that is a truncated Crockford32 encoded hash of the various
attributes of the denomination key (relative validity periods, fee
structure and key size). Thus, if any attributes of a coin change,
the name of the subdirectory will also change, even if the
denomination remains the same.
Within this subdirectory, each file represents a particular
denomination key. The filename is the starting time at which the
signing key can be used in microseconds since the Epoch. The
format on disk begins with a
@cite{struct TALER_EXCHANGEDB_DenominationKeyInformationP} giving
the attributes of the denomination key and the associated
signature with the exchange's long-term offline key:
@example
struct TALER_EXCHANGEDB_DenominationKeyInformationP @{
struct TALER_MasterSignatureP signature;
struct TALER_DenominationKeyValidityPS properties;
@};
@end example
This is then followed by the variable-size RSA private key in
libgcrypt's S-expression format, which can be decoded using
@cite{GNUNET_CRYPTO_rsa_private_key_decode()}.
@menu
* Revocations::
@end menu
@node Revocations
@subsection Revocations
@cindex payback
@cindex revocation
When an exchange goes out of business or detects that the private
key of a denomination key pair has been compromised, it may revoke
some or all of its denomination keys. At this point, the hashes
of the revoked keys must be returned as part of the @code{/keys} response
under ``payback''. Wallets detect this, and then return unspent
coins of the respective denomination key using the @code{/payback}
API.
When a denomination key is revoked, a revocation file is placed
into the respective subdirectory of ``denomkeys/''. The file has the
same prefix as the file that stores the
@cite{struct TALER_EXCHANGEDB_DenominationKeyInformationP} information,
but is followed by the ``.rev'' suffix. It contains a 64-byte
EdDSA signature made with the master key of the exchange with purpose
@code{TALER_SIGNATURE_MASTER_DENOMINATION_KEY_REVOKED}. If such a file
is present, the exchange must check the signature and if it is valid
treat the respective denomination key as revoked.
Revocation files can be generated using the
@code{taler-exchange-keyup} command-line tool using the @code{-r}
option. The Taler auditor will instruct operators to generate
revocations if it detects a key compromise (which is possible more
coins of a particular denomination were deposited than issued).
It should be noted that denomination key revocations should only happen
under highly unusual (``emergency'') conditions and not under normal
conditions.
@node Auditor signature storage
@section Auditor signature storage
Signatures from auditors are stored in the directory specified
in the exchange configuration section "exchangedb" under the
option "AUDITOR_BASE_DIR". The exchange does not care about
the specific names of the files in this directory.
Each file must contain a header with the public key information
of the auditor, the master public key of the exchange, and
the number of signed denomination keys:
@example
struct AuditorFileHeaderP @{
struct TALER_AuditorPublicKeyP apub;
struct TALER_MasterPublicKeyP mpub;
uint32_t dki_len;
@};
@end example
This is then followed by @cite{dki_len} signatures of the auditor of type
@cite{struct TALER_AuditorSignatureP}, which are then followed by another
@cite{dki_len} blocks of type @cite{struct TALER_DenominationKeyValidityPS}.
The auditor's signatures must be signatures over the information of
the corresponding denomination key validity structures embedded in a
@cite{struct TALER_ExchangeKeyValidityPS} structure using the
@cite{TALER_SIGNATURE_AUDITOR_EXCHANGE_KEYS} purpose.
@c **********************************************************
@c ******************* Appendices *************************
@c **********************************************************
@node GNU-AGPL
@chapter GNU Affero GPL
@cindex license
@include agpl.texi
@node GNU-FDL
@chapter GNU Free Documentation License
@cindex license
@include fdl-1.3.texi
@node Concept Index
@chapter Concept Index
@printindex cp
@bye