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updates sec 1-3

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Christian Grothoff 2016-08-25 16:56:31 +02:00
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articles/ui/ui.tex
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@ -131,7 +131,7 @@ micropayment system, which is not backed by a ``crypto currency''.
Payment systems involving state-issued currencies have been used for Payment systems involving state-issued currencies have been used for
centuries to facilitate transactions, and the involvement of the state centuries to facilitate transactions, and the involvement of the state
has been critical as state institutions can dampen fluctuations in the has been critical as state institutions can dampen fluctuations in the
value of the currency.~\cite{dominguez1993} Controlling money supply value of the currency~\cite{dominguez1993}. Controlling money supply
is critical to ensure stable prices that facilitate is critical to ensure stable prices that facilitate
trade~\cite{quantitytheory1997volckart} instead of speculation~\cite{lewis_btc_is_junk}. trade~\cite{quantitytheory1997volckart} instead of speculation~\cite{lewis_btc_is_junk}.
@ -216,7 +216,7 @@ based on resources from the W3C payment interest group.
Cash has traditionally circulated by being passed directly from buyers Cash has traditionally circulated by being passed directly from buyers
to sellers with each seller then becoming a buyer. Thus, cash is 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 the both buyer and seller roles, just at different times. appear in both buyer and seller roles, just at different times.
However, this view is both simplified and However, this view is both simplified and
somewhat dated. somewhat dated.
@ -251,7 +251,7 @@ to the amount of cash that they carry or accept at a given
time~\cite{Bankrate}. Additionally, customers are advised to choose time~\cite{Bankrate}. Additionally, customers are advised to choose
the ATMs they use carefully, as malicious ATMs may attempt to the ATMs they use carefully, as malicious ATMs may attempt to
{\em steal} their customer's credentials~\cite{ECB:TRoCF2014}. Authentication with an {\em steal} their customer's credentials~\cite{ECB:TRoCF2014}. Authentication with an
TM can involve a special ATM card, or the use of credit or ATM can involve a special ATM card, or the use of credit or
debit cards. In all these cases, these physical security tokens are debit cards. In all these cases, these physical security tokens are
issued by the customer's bank. issued by the customer's bank.
@ -269,26 +269,30 @@ issued by the customer's bank.
Credit and debit card payments operate by the customer providing their Credit and debit card payments operate by the customer providing their
credentials to the merchant. Many different authentication and credentials to the merchant. Many different authentication and
authorization schemes are in use in various combinations including authorization schemes are in use in various combinations. Secure
both secret information, which are usually PINs, and physical security systems typically combine multiple forms of authentication including
devices such as TANs~\cite{kobil2016tan}, cards with an EMV secret information, such as personal identification numbers (PINs),
chip~\cite{emv}, and the customer's mobile phone~\cite{mtan}. A transaction numbers (TANs)~\cite{kolbil2016tan} or credit card
typical modern Web payment process involves: {(1.)} the merchant verification (CCV) codes, and physical security devices such cards
offering a secure communication channel using TLS based on the X.509 with an EMV chip~\cite{emv}, TAN generators, or the customer's mobile
public key infrastructure;\footnote{Given numerous TLS protocol and phone~\cite{mtan}. A typical modern Web payment process involves:
implementation flaws as well as X.509 key management incidents in {(1.)} the merchant offering a secure communication channel using TLS
recent years~\cite{holz2014}, one cannot generally assume that the based on the X.509 public key infrastructure;\footnote{Given numerous
security provided by TLS is adequate under all circumstances.} TLS protocol and implementation flaws as well as X.509 key
{(2.)} selecting a {\em payment method}; {(3.)} entering the credit management incidents in recent years~\cite{holz2014}, one cannot
card details like the owner's name, card number, expiration time, CVV generally assume that the security provided by TLS is adequate under
code, and billing address; and {(4.)} (optionally) authorizing the all circumstances.} {(2.)} selecting a {\em payment method}; {(3.)}
transaction via mobile TAN, or by authenticating against the entering the credit card details like the owner's name, card number,
customer's bank, often on a Web site that is operated by the payment expiration time, CCV code, and billing address; and {(4.)}
processor and {\em not} the customer's bank. Figure~\ref{fig:cc3ds} (optionally) authorizing the transaction via mobile TAN, or by
shows a typical card-based payment process on the Web using the authenticating against the customer's bank. Due to the complexity
UML style of the W3C payment interest group~\cite{pigs}. Most of the details of this the data entry is often performed on a Web site that
are not relevant to this paper, but the diagram nicely illustrates the is operated by a third-party payment processor and {\em not} the merchant or
complexity of the common 3-D secure (3DS) process. 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.
Given this process, there is an inherent risk of information leakage Given this process, there is an inherent risk of information leakage
of customers' credentials. {\em Fraud detection} systems attempt to detect of customers' credentials. {\em Fraud detection} systems attempt to detect
@ -383,7 +387,7 @@ details into a peer-to-peer application. The user would access their
Bitcoin {\em wallet} and instruct it to transfer a particular amount Bitcoin {\em wallet} and instruct it to transfer a particular amount
from one of his accounts to the account of the merchant. He could from one of his accounts to the account of the merchant. He could
possibly include additional metadata to be associated with the possibly include additional metadata to be associated with the
transfer and embedded into the global public ledger. The wallet transfer to be embedded into the global public ledger. The wallet
application would then transmit the request to the Bitcoin application would then transmit the request to the Bitcoin
peer-to-peer overlay network. The use of an external payment peer-to-peer overlay network. The use of an external payment
application makes payments significantly less application makes payments significantly less
@ -443,7 +447,7 @@ globally on
average.\footnote{\url{http://hackingdistributed.com/2016/08/04/byzcoin/}} average.\footnote{\url{http://hackingdistributed.com/2016/08/04/byzcoin/}}
There are a variety of efforts to confront Bitcoin's scaling problems There are a variety of efforts to confront Bitcoin's scaling problems
with off-blockchain techniques, like side-chains. % \cite{???} with off-blockchain techniques, like side-chains. % \cite{???}
Amongst these, the Blind Off-chain Lightweight Transactions (BOLT) Amongst these, the blind off-chain lightweight transactions (BOLT)
proposal~\cite{BOLT} provides anonymity by routing off-blockchain proposal~\cite{BOLT} provides anonymity by routing off-blockchain
transfers through bank-like intermediaries. Although interesting, transfers through bank-like intermediaries. Although interesting,
there are numerous seemingly fragile aspects of the BOLT protocol, there are numerous seemingly fragile aspects of the BOLT protocol,
@ -506,7 +510,7 @@ anti-corruption efforts.
Taler achieves anonymity for buyers using {\em blind Taler achieves anonymity for buyers using {\em blind
signatures}~\cite{chaum1983blind}. Since their discovery thirty years signatures}~\cite{chaum1983blind}. Since their discovery thirty years
ago, cryptographers have viewed blind signatures as the optimal ago, cryptographers have viewed blind signatures as the optimal
cryptographic primitive for consumer-level transaction systems. cryptographic primitive for privacy-preserving consumer-level transaction systems.
However, previous transaction systems based on blind signatures have However, previous transaction systems based on blind signatures have
failed to see widespread adoption. This paper details strategies for failed to see widespread adoption. This paper details strategies for
hiding the cryptography from users and integrating smoothly with the hiding the cryptography from users and integrating smoothly with the
@ -515,7 +519,7 @@ cryptography and real-world deployment.
%\subsection{Design overview} %\subsection{Design overview}
\begin{figure}[t!] \begin{figure}[b!]
\centering \centering
\begin{tikzpicture} \begin{tikzpicture}
\tikzstyle{def} = [node distance=3em and 5em, inner sep=1em, outer sep=.3em]; \tikzstyle{def} = [node distance=3em and 5em, inner sep=1em, outer sep=.3em];
@ -538,7 +542,7 @@ cryptography and real-world deployment.
\end{figure} \end{figure}
There are four components of the Taler system (Figure~\ref{fig:system}): There are four key roles in the Taler system (Figure~\ref{fig:system}):
\begin{figure*}[b!] \begin{figure*}[b!]
\includegraphics[width=0.9\textwidth]{figs/taler-withdraw.pdf} \includegraphics[width=0.9\textwidth]{figs/taler-withdraw.pdf}
@ -552,14 +556,14 @@ There are four components of the Taler system (Figure~\ref{fig:system}):
\begin{itemize} \begin{itemize}
\item \item
{\em Customers} use a digital wallet to withdraw, {\em Customers} use a digital wallet to withdraw,
hold, and spend coins. Wallets also manage the customer's accounts hold, and spend coins. Wallets manage the customer's accounts
at the exchange, and keep receipts in a transaction history. Wallets can be at the exchange, and keep receipts in a transaction history. Wallets can be
realized as browser extensions, mobile Apps or even in custom realized as browser extensions, mobile Apps or even in custom
hardware. If a user's digital wallet is compromised, the current 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 like with an ordinary wallet containing cash.
A wallet also includes a list of acceptable auditors, and will warn A wallet includes a list of trusted auditors, and will warn
users against using an exchange that is not certified by one of these users against using an exchange that is not certified by a trusted
auditors. auditor.
\begin{figure}[t!]%[36]{R}{0.5\linewidth} \begin{figure}[t!]%[36]{R}{0.5\linewidth}
\subfloat[Bank login. (Simplified for demonstration.)]{ \subfloat[Bank login. (Simplified for demonstration.)]{
@ -610,9 +614,9 @@ Web shops and point-of-sale systems.
{\em Auditors} verify that exchanges operate correctly to limit the risk {\em Auditors} verify that exchanges operate correctly to limit the risk
that customers and merchants incur by using a particular exchange. that customers and merchants incur by using a particular exchange.
Auditors are typically operated by or on behalf of financial regulatory authorities. Auditors are typically operated by or on behalf of financial regulatory authorities.
Depending on local legislation, auditors mandate that exchanges Depending on local legislation, auditors may mandate that exchanges
have enough financial reserves before authorizing them to create a given have enough financial reserves before authorizing them to create a given
volume of signed digital coins in order to compensate for potential risks due to volume of signed digital coins to provide a buffer against potential risks due to
operational failures (such as data loss or theft of private keys) of the exchange. operational failures (such as data loss or theft of private keys) of the exchange.
Auditors certify exchanges that they audit using digital signatures. The Auditors certify exchanges that they audit using digital signatures. The
respective signing keys of the auditors are distributed to customer and respective signing keys of the auditors are distributed to customer and