expand security discussion in paper

2 files changed, 78 insertions, 18 deletions

diff --git a/doc/paper/taler.bib b/doc/paper/taler.bib
index a7d6f6816..a9bf95d48 100644
--- a/doc/paper/taler.bib
+++ b/doc/paper/taler.bib
@@ -36,6 +36,47 @@
   year =      {2015},
 }
 
+
+@Misc{fatf1997,
+  title =     {FATF-IX report on money laundering typologies},
+  howpublished = {\url{http://www.fatf-gafi.org/media/fatf/documents/reports/1996%201997%20ENG.pdf}},
+  month =     {feb},
+  year =      {1998},
+}
+
+@TechReport{,
+  author =       {},
+  title =        {},
+  institution =  {},
+  year =         {},
+  OPTkey =       {},
+  OPTtype =      {},
+  OPTnumber =    {},
+  OPTaddress =   {},
+  OPTmonth =     {},
+  OPTnote =      {},
+  OPTannote =    {}
+}
+
+@InProceedings{sander1999escrow,
+  author =       {Tomas Sander and Amnon Ta-Shma},
+  title =        {On Anonymous Electronic Cash and Crime},
+  booktitle = {ISW'99},
+  year =      {1999},
+  series =    {LNCS 1729},
+  pages =     {202--206},
+}
+
+@Article{solms1992perfect,
+  author =       {Sebastiaan H. von Solms and David Naccache},
+  title =        {On blind signatures and perfect crimes},
+  journal = {Computers \& Security},
+  year =      {1992},
+  volume =    {11},
+  number =    {6},
+  pages =     {581--583},
+}
+
 @inproceedings{chaum1990untraceable,
   title={Untraceable electronic cash},
   author={Chaum, David and Fiat, Amos and Naor, Moni},
diff --git a/doc/paper/taler.tex b/doc/paper/taler.tex
index 199de85e4..c504e843f 100644
--- a/doc/paper/taler.tex
+++ b/doc/paper/taler.tex
@@ -923,6 +923,31 @@ that is unlinkable to the refunded transaction.
 
 \section{Discussion}
 
+Taler's security is largely equivalent to that of Chaum's original
+design without online checks (and without the cut-and-choose
+revelation of double-spending customers for offline spending).  We
+specifically note that the digital equivalent of the ``Columbian Black
+Market Exchange''~\cite{fatf1997} is a theoretical problem for both
+Chaum and Taler, as individuals with a strong mutual trust foundation
+can simply copy electronic coins and thereby establish a limited form
+of black transfers.  However, unlike the situation with physical
+checks with blank recipients in the Columbian black market, the
+transitivity is limited as each participant can deposit the electronic
+coins and thereby cheat any other participant, while in the Columbian
+black market each participant only needs to trust the issuer of the
+check and not also all previous owners of the physical check.
+
+As with any unconditionally anonymous payment system, the ``Perfect
+Crime'' attack~\cite{solms1992perfect} where blackmail is used to
+force the mint to issue anonymous coins also continues to apply in
+principle.  However, as mentioned Taler does faciliate limits on
+withdrawals, which we believe is a better trade-off than the
+problematic escrow systems where the necessary intransparency
+actually facilitates voluntary cooperation between the mint and
+criminals~\cite{sander1999escrow} and where state can selectively
+deanonymize activists to support the deep state's quest for absolute
+security.
+
 \subsection{Offline Payments}
 
 Chaum's original proposals for anonymous digital cash avoided the need
@@ -952,28 +977,22 @@ currency.  A tax auditor can then request the merchant to reveal
 (meaningful) details about the business transaction ($\mathcal{D}$,
 $a$, $p$, $r$), including proof that applicable taxes were paid.
 
-If a merchant is not able to provide theses values, he can be punished
-in relation to the amount transferred by the traditional currency
-transfer.
-
+If a merchant is not able to provide theses values, he can be
+subjected to financial penalties by the state in relation to the
+amount transferred by the traditional currency transfer.
 
-\section{Future Work}
 
-%The legal status of the system needs to be investigated in the various
-%legal systems of the world.  However, given that the system enables
-%taxation and is able to impose withdrawal limits and thus is not
-%suitable for money laundering, we are optimistic that states will find
-%the design desirable.
+\subsection{System Performance}
 
 We performed some initial performance measurements for the various
-operations.  The main conclusion was that the computational and
-bandwidth cost for transactions described in this paper is smaller
-than $10^{-3}$ cent/transaction, and thus dwarfed by the other
-business costs for the mint.  However, this figure excludes the cost
-of currency transfers using traditional banking, which a mint operator
-would ultimately have to interact with.  Here, mint operators should
-be able to reduce their expenses by aggregating multiple transfers to
-the same merchant.
+operations on our mint implementation.  The main conclusion was that
+the computational and bandwidth cost for transactions described in
+this paper is smaller than $10^{-3}$ cent/transaction, and thus
+dwarfed by the other business costs for the mint.  However, this
+figure excludes the cost of currency transfers using traditional
+banking, which a mint operator would ultimately have to interact with.
+Here, mint operators should be able to reduce their expenses by
+aggregating multiple transfers to the same merchant.
 
 
 \section{Conclusion}