krista pass
This commit is contained in:
parent
5e595863bd
commit
f88abffb28
@ -141,8 +141,9 @@ transactions involving the exchange of physical goods. Consequently,
|
||||
if we want to associate payments with these types of transactions, we
|
||||
face the challenge of reducing the mental and technical overheads of
|
||||
existing payment systems. For example, executing a 3DS payment
|
||||
process (Figure~\ref{fig:cc3ds}) takes too long, is way too complex
|
||||
and way to expensive to be used for payment for typical Web articles.
|
||||
process (Figure~\ref{fig:cc3ds}) takes too long, is way too complex,
|
||||
and way too expensive to be used for payment for typical Web articles.
|
||||
%KG: Define 3DS. I have no idea WTF you're talking about throughout the paper with this.
|
||||
|
||||
Addressing this problem is urgent: ad-blocking technology is eroding
|
||||
advertising as a substitute for micropayments~\cite{adblockblocks},
|
||||
@ -166,23 +167,23 @@ means that for any transaction the state can easily obtain the
|
||||
necessary information about the identity of the merchant and the
|
||||
respective contract in order to levy income, sales, or value-added
|
||||
taxes. Taler uses blind signatures~\cite{chaum1983blind} to create
|
||||
digital coins, and a new {\em refresh} protocol~\cite{talercrypto} to
|
||||
digital coins and a new {\em refresh} protocol~\cite{talercrypto} to
|
||||
allow giving change and refunds while maintaining unlinkability.
|
||||
|
||||
This paper will not consider the details of Taler's cryptographic
|
||||
protocols.\footnote{Details of the protocol are documented at
|
||||
\url{https://api.taler.net/}} The basic cryptography behind
|
||||
blind-signature based payment systems has been known for over 25
|
||||
years~\cite{chaum1990untraceable}. However, only in 2015 the W3c
|
||||
years~\cite{chaum1990untraceable}. However, it was not until 2015 that the W3C
|
||||
started the payments working group~\cite{pigs} to explore requirements
|
||||
for deploying payment systems that are more secure and easy to use for
|
||||
the Web. Our work describes how a modern payment system using blind
|
||||
signatures could practically be integrated with the modern Web to
|
||||
improve usability, security and privacy. This includes the challenge
|
||||
improve usability, security, and privacy. This includes the challenge
|
||||
of hiding the cryptography from the users, integrating with modern
|
||||
browsers, integrating with Web shops, providing proper cryptographic
|
||||
proofs for all operations, and handling network failures. We explain
|
||||
our design using terms from existing {\em mental models} users have
|
||||
our design using terms from existing {\em mental models} that users have
|
||||
from widespread payment systems.
|
||||
|
||||
%\newpage
|
||||
@ -215,7 +216,7 @@ based on resources from the W3C payment interest group.
|
||||
|
||||
Cash has traditionally circulated by being passed directly from buyers
|
||||
to sellers with each seller then becoming a buyer. Thus, cash is
|
||||
inherently a {\em peer-to-peer} payment system as participants all
|
||||
inherently a {\em peer-to-peer} payment system, as participants all
|
||||
appear in both buyer and seller roles, just at different times.
|
||||
However, this view is both simplified and
|
||||
somewhat dated.
|
||||
@ -246,7 +247,7 @@ for the customer. Instead, the merchant provides paper
|
||||
{\em receipts}, which are generated independently and do not receive
|
||||
the same anti-forgery protections that are in place for cash.
|
||||
|
||||
Against most attacks, customers and merchants {\em limit} their risks
|
||||
Against most attacks, customers and merchants {\em limit} their risk
|
||||
to the amount of cash that they carry or accept at a given
|
||||
time~\cite{Bankrate}. Additionally, customers are advised to choose
|
||||
the ATMs they use carefully, as malicious ATMs may attempt to
|
||||
@ -266,6 +267,7 @@ issued by the customer's bank.
|
||||
\caption{Card payment processing with 3DS. (From: W3C Web Payments IG.)}
|
||||
\label{fig:cc3ds}
|
||||
\end{figure*}
|
||||
%KG: I hope they can print this larger, because this is WAY too small to be of any use.
|
||||
|
||||
Credit and debit card payments operate by the customer providing their
|
||||
credentials to the merchant. Many different authentication and
|
||||
@ -286,13 +288,14 @@ entering the credit card details like the owner's name, card number,
|
||||
expiration time, CCV code, and billing address; and {(4.)}
|
||||
(optionally) authorizing the transaction via mobile TAN, or by
|
||||
authenticating against the customer's bank. Due to the complexity
|
||||
of this the data entry is often performed on a Web site that
|
||||
of this, the data entry is often performed on a Web site that
|
||||
is operated by a third-party payment processor and {\em not} the merchant or
|
||||
the customer's bank. Figure~\ref{fig:cc3ds} shows a typical card-based payment
|
||||
process on the Web using the UML style of the W3C payment interest
|
||||
group~\cite{pigs}. Most of the details are not relevant to this
|
||||
paper, but the diagram nicely illustrates the complexity of the common
|
||||
3-D secure (3DS) process.
|
||||
%KG: Define 3DS the FIRST time you use it.
|
||||
|
||||
Given this process, there is an inherent risk of information leakage
|
||||
of customers' credentials. {\em Fraud detection} systems attempt to detect
|
||||
@ -325,9 +328,9 @@ malicious merchants to later change the terms of the contract.
|
||||
Beyond these primary issues, customers face secondary risks of
|
||||
identity theft from the personal details exposed by the authentication
|
||||
procedures. In this case, even if the financial damages are ultimately
|
||||
covered by the bank, the customer always has to deal with the hassle
|
||||
covered by the bank, the customer always has to deal with the procedure
|
||||
of {\em notifying} the bank in the first place. As a result,
|
||||
customers must remain wary about using their card, which limits their
|
||||
customers must remain wary about using their cards, which limits their
|
||||
online shopping~\cite[p. 50]{ibi2014}.
|
||||
% There is nevertheless a trend towards customers preferring cards
|
||||
% over cash even in face-to-face purchases \cite{} in part because
|
||||
@ -515,7 +518,7 @@ ago, cryptographers have viewed blind signatures as the optimal
|
||||
cryptographic primitive for privacy-preserving consumer-level transaction systems.
|
||||
However, previous transaction systems based on blind signatures have
|
||||
failed to see widespread adoption. This paper details strategies for
|
||||
hiding the cryptography from users and integrating smoothly with the
|
||||
hiding the complexity of the cryptography from users and integrating smoothly with the
|
||||
Web, thereby providing crucial steps to bridge the gap between good
|
||||
cryptography and real-world deployment.
|
||||
|
||||
@ -562,7 +565,7 @@ hold, and spend coins. Wallets manage the customer's accounts
|
||||
at the exchange, and keep receipts in a transaction history. Wallets can be
|
||||
realized as browser extensions, mobile Apps or even in custom
|
||||
hardware. If a user's digital wallet is compromised, the current
|
||||
balance may be lost, just like with an ordinary wallet containing cash.
|
||||
balance may be lost, just as with an ordinary wallet containing cash.
|
||||
A wallet includes a list of trusted auditors, and will warn
|
||||
users against using an exchange that is not certified by a trusted
|
||||
auditor.
|
||||
@ -591,9 +594,9 @@ auditor.
|
||||
customers to withdraw anonymous digital coins,
|
||||
and merchants to deposit digital coins, in exchange for
|
||||
bank money. Coins are signed by the exchange using
|
||||
a blind signing scheme~\cite{chaum1983blind}. Thus, only
|
||||
a blind signature scheme~\cite{chaum1983blind}. Thus, only
|
||||
an exchange can issue new coins, but coins cannot be traced back
|
||||
to the customer that withdrew them.
|
||||
to the customer who withdrew them.
|
||||
Furthermore, exchanges learn the amounts withdrawn by customers
|
||||
and deposited by merchants, but they do not learn the relationship
|
||||
between customers and merchants. Exchanges perform online detection
|
||||
@ -606,7 +609,7 @@ by customers' wallets. Merchants deposit these coins at the
|
||||
exchange used by the customer in return for a bank wire
|
||||
transfer of their value. While the exchange is determined by
|
||||
the customer, the merchant's contract specifies the currency,
|
||||
a list of accepted auditors and the maximum exchange deposit
|
||||
a list of accepted auditors, and the maximum exchange deposit
|
||||
fee the merchant is willing to pay. Merchants consist of a
|
||||
{\em frontend}, which interacts with the customer's wallet, and a {\em
|
||||
backend}, which interacts with the exchange. Typical frontends include
|
||||
@ -653,7 +656,7 @@ operation. Restarting the browser is not required.
|
||||
As with cash, the customer must first withdraw digital coins
|
||||
(Figure~\ref{fig:taler-withdraw}). For this, the customer must first
|
||||
visit the bank's online portal. Here, the bank will
|
||||
typically require some form of authentication, the specific method
|
||||
typically require some form of authentication; the specific method
|
||||
used depends on the bank (Figure~\ref{subfig:login}).
|
||||
|
||||
The next step depends on the level of Taler support offered by the bank:
|
||||
@ -671,8 +674,8 @@ The next step depends on the level of Taler support offered by the bank:
|
||||
54-character reserve key, which includes 256 bits of entropy and an
|
||||
8-bit checksum into the transfer subject. Naturally, the above is
|
||||
exactly the kind of interaction we would like to avoid for
|
||||
usability reason.
|
||||
\item Hence, if the bank fully supports Taler, the
|
||||
usability reasons.
|
||||
\item Otherwise, if the bank fully supports Taler, the
|
||||
customer has a form in the online banking portal in which they can specify
|
||||
an amount to withdraw (Figure~\ref{subfig:withdraw}).
|
||||
The bank then triggers an interaction with
|
||||
@ -1547,7 +1550,7 @@ at \url{https://demo.taler.net/}.
|
||||
This work benefits from the financial support of the Brittany Region
|
||||
(ARED 9178) and a grant from the Renewable Freedom Foundation. We
|
||||
thank Bruno Haible for his financial support enabling us to
|
||||
participate with the W3c payment working group. We thank the W3c
|
||||
participate with the W3c payment working group. We thank the W3C
|
||||
payment working group for insightful discussions about Web payments.
|
||||
We thank Krista Grothoff and Neal Walfield for comments on an earlier
|
||||
draft of the paper. We thank Gabor Toth for his help with the
|
||||
|
Loading…
Reference in New Issue
Block a user