Dissent - Dining-Cryptographers, Shuffled-Send Network

Overview

This library will eventually provide a framework for constructing provably anonymous overlays with the following key features.

The library requires Qt and CryptoPP and can be built using qmake on dissent.pro (qmake dissent.pro)

While previous versions of the code focused on linkable libraries, because this has unnecessary complexities, we plan to only support unified binaries.

Directory Structure

• ext - external sources required to build the code
• src - source code for the development branch
• src/Anonymous - Anonymity protocols
• src/Applications - User interfaces modules
• src/Connections - Message plane abstraction
• src/Crypto - Cryptography interface
• src/Identity - Containers for user information
• src/Identity/Authentication - Authentication protocols
• src/Messaging - Interfaces for abstracting communication
• src/Overlay - Manages connections
• src/Tests - Test code for classes in other folders
• src/Transports - Low level Networking interface
• src/Tunnel - SOCKS proxy
• src/Utils - Miscellaneous tools
• src/Web - Web server
• src/Web/Services - Web services
• legacy/libdissent - original, unmodified C++ version
• legacy/py - original, unmodified Python version

Using

Build the command-line (Application): qmake application.pro make

The default configuration will create a local overlay with 3 servers and 20 clients, to use it execute: cd conf/local && ln -s ../../dissent . && ./run_all.sh

This will launch a command-line interface, where commands can be typed. (Note: by default logging is enabled, the above redirects it to /dev/null)

Type help to print out the commands.

Dissent also supports command-line flags. Type: ./dissent With no parameters or with --help to get a list of optional parameters.

Command Line Network Use

Inspect conf/slave_tcp.conf and conf/master_tcp.conf

Nodes using conf/master_tcp.conf are bootstrap peers Nodes using conf/slave_tcp.conf should have bootstrap peers end points in their remote_peers list

Binding to 0.0.0.0 will result in the first non-loop backdevice IP address being used in exchanging IP address information.

After changing the configuration files and distributing the application, begin by turning on the bootstrap peers first and then the client peers. Afterward interaction is the same as discussed in the "Using" section.

Web Server Use

See WEB_USE in the top level directory (same as the README)

Proxy Server Use

Inspect conf/tunnel-entry.conf and conf/tunnel-exit.conf

Dissent has a built-in SOCKS 5 server for tunneling TCP traffic through a Dissent session. SOCKS tunneling requires two special nodes: an entry node and an exit node. The entry node runs the SOCKS server and inserts SOCKS traffic into a Dissent session. The exit node receives SOCKS traffic from a Dissent session and forwards it to its destination.

To enable a SOCKS entry node, add these lines to your .conf file: entry_tunnel = true entry_tunnel_url = "tcp://socks_server_ip:port" If the socks_server_ip is 0.0.0.0, then the SOCKS server will listen on any hostname.

The SOCKS server handles only TCP traffic, but it can resolve hostname-type addresses.

To enable a SOCKS exit node, add this line to your .conf file: exit_tunnel = true

Tests

This suite contains many tests using googletest[1], use qmake on test.pro (qmake test.pro && make && ./test) to generate an appropriate makefile, which will create a binary to test the code.

googletest was chosen because testing system code with QtTest would be quite inefficient.

1 - http://code.google.com/p/googletest/

Key generation

Dissent supports BER decoding and writes in DER encoding[1], this apparently provides the best interoperability. To create public and private keys, we have provided a tool called keygen (qmake keygen.pro && make && ./keygen), that can create public / private key pairs and save them as a hash of the public key. This hash can then be used as the Id of the node in Dissent.

1 - http://www.cryptopp.com/wiki/Keys_and_Formats#BER_and_DER_Encoding

Logging and Debugging Output

Logging outputs are compiled in by default but can be disabled by uncommenting the following lines in test.pro and console.pro: #DEFINES += QT_NO_DEBUG_OUTPUT #DEFINES += QT_NO_WARNING_OUTPUT

Logging can be manipulated by using the Dissent::Utils::Logging class. For the ConsoleApp this is done by using the Settings file (conf).

To send logging output to standard error use log = "stderr". To send logging output to standard output use log = "stdout". To send logging output to a file use log = "filename". To disable logging use log = "" or exclude log altogether.

Links

Dedis -- Research group at Yale producing this software -- http://dedis.cs.yale.edu/ Dissent -- Overview of the protocol -- http://dedis.cs.yale.edu/2010/anon/

Contact

TBA

Workflow

More specifically, these are requirements that should be followed prior to asking for a code review / pull. A code review / pull in this sense refers to the submission of a pull request not an academic discussion on design choices.

API expectations:

• Doxygen with comments
• Follows existing patterns in the code or accompanies patches that improve those interfaces

Internals:

• Minimizes dependencies, if A can work without knowing about B, A should not know about B, make a C that knows about both to handle interoperation
• Emphasize Qt features while minimizing additional dependencies on external libraries
• Avoid blocking calls

Commits:

• The comments should be clear and only code chunks relevant to the commit message should be included
• Merges should be rebased onto the current master and tested working before merging (git checkout -b merge master && git merge --squash dev)
• Incomplete work should not be committed nor merged

Also note, when you submit code for inclusion in this library, you implicitly release your personal license to the software to Yale Dedis, see below.

License

While the code linked relies on a variety of licenses, which must be respected, the code contained herein shall use the following license:

Copyright (C) 2011 Yale Dedis

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 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 General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.