[taler-anastasis] 01/02: some fixes

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dennis-neufeld pushed a commit to branch master
in repository anastasis.

commit a35480f731bb549b8f3d1aa0f4b4bb59862bf704
Author: Dennis Neufeld <dennis.neufeld@students.bfh.ch>
AuthorDate: Tue Jun 2 15:53:01 2020 +0000

    some fixes
---
 doc/thesis/bibliothek.bib                 |   2 +-
 doc/thesis/images/system-architecture.png | Bin 0 -> 137904 bytes
 doc/thesis/implementation.tex             |  16 ++++++++--------
 doc/thesis/related_work.tex               |  13 ++++++-------
 4 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/doc/thesis/bibliothek.bib b/doc/thesis/bibliothek.bib
index cc95d28..eb76b9e 100644
--- a/doc/thesis/bibliothek.bib
+++ b/doc/thesis/bibliothek.bib
@@ -223,7 +223,7 @@
   title={Alterable application specific integrated circuit (ASIC)},
   author={Madurawe, Raminda Udaya},
   year={2006},
-  month=jun # "~20",
+  month=6,
   publisher={Google Patents},
   note={US Patent 7,064,579}
 }
diff --git a/doc/thesis/images/system-architecture.png 
b/doc/thesis/images/system-architecture.png
new file mode 100644
index 0000000..6243799
Binary files /dev/null and b/doc/thesis/images/system-architecture.png differ
diff --git a/doc/thesis/implementation.tex b/doc/thesis/implementation.tex
index 79ca1f8..8a87109 100644
--- a/doc/thesis/implementation.tex
+++ b/doc/thesis/implementation.tex
@@ -1,7 +1,7 @@
 \section{Implementation}
 The whole Anastasis software is written in C. We decided to use C because of 
the various cryptographic libraries and the available documentations.
-Additionaly GNU Taler and Sync which are working close with anastasis are also 
written in C. This makes the integration of our application much easier.\\
-The whole Anastasis application consits of multiple components. On the 
following
+Additionally GNU Taler and Sync which are working close with Anastasis are 
also written in C. This makes the integration of our application much easier.\\
+The whole Anastasis application consists of multiple components. On the 
following
 graphic is a overview over all the components in Anastasis. \\
 \begin{figure}[H]
        \centering
@@ -9,7 +9,7 @@ graphic is a overview over all the components in Anastasis. \\
        \caption{Secret split process}
        \label{fig:secret_split}
 \end{figure}
-On the left are some of the planed authentication methods from the 
application. On the right side of the box are the core parts which are 
neccessary to operate Anastasis commercialy, these parts are planned for the 
future and not part of this thesis. \\ 
+On the left are some of the planed authentication methods from the 
application. On the right side of the box are the core parts which are 
necessary to operate Anastasis commercially, these parts are planned for the 
future and not part of this thesis. \\ 
 At the bottom section are the external libraries used for the project. These 
libraries are presented in the section Libraries. \\
 In the center is the core implementation of Anastasis.
 
@@ -44,9 +44,9 @@ This section describes a happy flow of the two protocols of 
Anastasis, key split
 \begin{enumerate}
 \item The user selects a server on which he previously stored a recovery 
document.
 \item Next the client downloads the server salt to compute the server specific 
account public key(GET /salt). 
-\item After the user generated the public key he will downlaod the recovery 
document. At this point he can define if he wants a specific version or the 
latest version of the recovery document. In the graphic the client downloads 
the latest version(GET /policy/\$ACCOUNT\_PUB).
+\item After the user generated the public key he will download the recovery 
document. At this point he can define if he wants a specific version or the 
latest version of the recovery document. In the graphic the client downloads 
the latest version(GET /policy/\$ACCOUNT\_PUB).
 \item The clien will now decrypt the recovery document and list all policies 
and authentication methods. The user now has to solve these challenges. For 
example he has to answer a secure question or he has to type in a pin which was 
sent to him by SMS.(GET /truth/\$UUID?resonse=\$RESPONSE \\ 
-After each successfully solved challenge the client will check if one of the 
policies is fullfilled. If one of the policies is finished, the client will 
decrypt the core secret and provide it to the user.
+After each successfully solved challenge the client will check if one of the 
policies is fulfilled. If one of the policies is finished, the client will 
decrypt the core secret and provide it to the user.
 \end{enumerate}
 
 \subsection{Libraries}
@@ -57,18 +57,18 @@ GNU Taler is one of the main reason why we started to 
implement Anastasis, since
 "GNU Taler is a privacy-preserving payment system. Customers can stay 
anonymous, but merchants can not hide their income through payments with GNU 
Taler. This helps to avoid tax evasion and money laundering."\cite{gnu_taler}  
\\
 To operate GNU Taler the user needs to install an electronic wallet. This 
wallet is secured with a private key. Here comes Anastasis into play, Anastasis 
will secure this private key for the user. \\ 
 In our implementation GNU Taler is also our payment system. We decided to use 
GNU Taler because both Anastasis and GNU Taler are privacy preserving 
applications. If we for example used credit cards for payments the user would 
no longer be anonymous which is a core part of Anastasis.
-Additionaly GNU Taler is in the GNU package, this means it will always remain 
free software.\cite{gnu_taler}
+Additionally GNU Taler is in the GNU package, this means it will always remain 
free software.\cite{gnu_taler}
 \subsubsection{PostgreSQL}
 PostgreSQL is a open source object-relational database. PostgreSQL has over 30 
years of active development which makes it a very stable and reliable software. 
\\
 We use PostgreSQL as our database on the Anastasis server. We decided to use 
PostgreSQL because its a open source and lightweight software which has a big 
community.
 This means there are alot of helpful documentations and 
forums.\cite{postgresql}
 \subsubsection{Libcurl}
 Libcurl is a free URL transfer library. Libcurl supports a wide range of 
protocols and a C API. Libcurl is also ready for IPv6 and SSL certificates. \\
-For Anastasis we use Libcurl to generate the client side HTTP requests. We 
decided to use Libcurl because it is also written in C and free software. The 
software is also well suported and has a good documentation.
+For Anastasis we use Libcurl to generate the client side HTTP requests. We 
decided to use Libcurl because it is also written in C and free software. The 
software is also well supported and has a good documentation.
 This makes the integration in our application very easy.\cite{libcurl}
 \subsubsection{GNU Libmicrohttpd}
 GNU libmicrottpd is a small C library which provides a easy way to run a HTTP 
server.
-We use GNU Libmicrohttpd in Anastasis to provide a simple webserver. The main 
reason why we didnt use apache or nginx is that we do not need a standalone 
webserver. The Anastasis webserver just has to handle some API requests, a 
standalone webserver is not needed for that and would make the infrastructure 
more complex to maintain and develop. Since GNU Libmicrohttpd is also part of 
the GNU project it will remain free software.\cite{libmicrohttpd}
+We use GNU Libmicrohttpd in Anastasis to provide a simple webserver. The main 
reason why we didn't use apache or nginx is that we do not need a standalone 
webserver. The Anastasis webserver just has to handle some API requests, a 
standalone webserver is not needed for that and would make the infrastructure 
more complex to maintain and develop. Since GNU Libmicrohttpd is also part of 
the GNU project it will remain free software.\cite{libmicrohttpd}
 
 \subsection{Testing}
 
diff --git a/doc/thesis/related_work.tex b/doc/thesis/related_work.tex
index 6401f32..d5919bb 100644
--- a/doc/thesis/related_work.tex
+++ b/doc/thesis/related_work.tex
@@ -52,29 +52,28 @@ In Anastasis the user is the trusted dealer who splits the 
secret and also recon
 \subsubsection{Shamir's Secret Sharing}
 The algorithm "Shamir's Secret Sharing" is one of the most well known secret 
sharing scheme. It „divide[s] data D into n pieces in such a way that D is 
easily reconstructible from any k pieces, but even complete knowledge of k - 1 
pieces reveals absolutely no information about D“ \cite{shamir_sharing}.\\
 Shamir’s simple secret sharing scheme has two key limitations. First, it 
requires a trusted dealer who initially generates the secret to be distributed, 
and second the shares are not verifiable during reconstruction. Therefore, 
malicious shareholders could submit corrupt shares to prevent the system from 
reconstructing the secret -- without these corrupt shareholders being 
detectable as malicious. Furthermore, the dealer distributing the shares could 
be corrupt and distribute some incons [...]
-Despite this, Shamir's Secret Sharing is inflexible because the "k out of 
n"-design and also is very inefficient for big n. For Anastasis we need a more 
flexible solution allowing other cases too. The user of Anastasis should be 
able to decide himself which combinations of \textit{players} shall be used. 
FIXME
+Despite this, Shamir's Secret Sharing is inflexible because the "k out of 
n"-design and also is very inefficient for big n. For Anastasis we need a more 
flexible solution allowing other cases too. The user of Anastasis should be 
able to decide himself which combinations of \textit{players} shall be used.
 
 \subsubsection{Verifiable Secret Sharing}
 Verifiability can be achieved by using so called commitment schemes like the 
Pederson commitment. It allows „to distribute a secret to n persons such that 
each person can verify that he has received correct information about the 
secret without talking with other persons“ \cite{pedersen_sharing_0}. In his 
paper „A Practical Scheme for Non-interactive Verifiable Secret Sharing“ 
\cite{feldman_sharing}, Paul Feldman  combines the two schemes Shamir Secret 
Sharing and Pederson commitment. His [...]
-Because in Anastasis we have a trusted dealer, the shares must not be verified 
and therefor we don't use VSS.
+Because in Anastasis we have a trusted dealer, the shares must not be verified 
and therefor we don't need VSS.
 
 \subsubsection{Distributed Key Generation}
 Distributed key generation algorithms, short DKG, solve the problem of needing 
a trustworthy dealer by relying on a threshold of honest persons. Contrary to 
the above-mentioned schemes, in distributed key generation algorithms every 
participant is involved in key generation.\\
 The Pederson DKG is such „a secret sharing scheme without a mutually trusted 
authority“ \cite{pedersen_sharing_5.2}. Basically, this DKG works as follows: \\
 First, each involved party generates a pre-secret and distributes it to all 
parties using the verifiable secret sharing scheme of Feldman.\\ 
-Afterwards, each party recombines the received shares, including its own 
pre-secret, to a share of the main secret. The main secret can be reconstructed 
by summing up each recombination of the shared pre-secrets.
+Afterwards, each party recombines the received shares, including its own 
pre-secret, to a share of the main secret. The main secret can be reconstructed 
by summing up each recombination of the shared pre-secrets.\\
+For Anastasis we do not need a DKG because the dealer is the user himself and 
therefore, he is fully trustworthy.
+
 
 \subsection{MIDATA}
 MIDATA is a project that aims to give patients back control over their medical 
data and to enable them to share their data only with those they trust 
\footnote{\url{https://www.midata.coop/}}. In case the patient lost his device 
running the MIDATA-application and his MIDATA-password, MIDATA build in a key 
recovery system using the Shamir Secret Sharing Scheme mentioned above. In 
their case a few "persons working at MIDATA have generated a public-private key 
pair (Recovery key) on their o [...]
-The security of MIDATA as described in ASDHJGSADJGH is broken in two ways:
+The security of MIDATA as described in "Patient empowerment in IoT for eHealth 
- How to deal with lost keys?" \cite{midata} is broken in two ways:
 \begin{enumerate}
        \item The password is reconstructed at the server, not at the patients 
device. An administrator of the server can theoretically access the recovered 
password at that time. A correct use of Shamir Secret Sharing scheme would 
reconstruct the password.
        \item It is not clear which authentication methods the persons working 
for MIDATA use for their decisions and activities regarding the key recovery. 
The business process used here could be vulnerable. For example, an attacker 
could use social engineering to illegitimately trigger a recovery process via 
e-mail if it is the chosen authentication method.
 \end{enumerate}
 
-\subsubsection{Key sharing in Anastasis}
-FIXMEFor Anastasis we do not need a DKG because the dealer is the user himself 
and therefore, he is fully trustworthy. But we need verifiability. In our case 
we achieve verifiability by using HMACs. Furthermore, for our purposes the 
above-mentioned algorithms are inadequate because we are dealing with a 
manageable number of sharing parties and we need a more flexible solution. FIXME
-
 
 \subsection{Authentication}
 Anastasis is designed to use a wide range of authentication methods to 
authenticate its users. There are several authentication methods available, a 
short overview of the methods is presented here. 

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