Verificatum Mix-Net (VMN)

Overview

VMN was completed 2008 and is the first implementation of a fully distributed and provably secure mix-net. It is also the first implementation of a universally verifiable mix-net and the first with a serious benchmark.

However, the framework is quite general and several of the subprotocols are useful without any changes to implement other complex protocols.

The software is modular and well documented to allow easy use and verification. For comprehensive information and documentation we refer the reader to https://www.verificatum.org.

Quick Start

An installation package is available at https://www.verificatum.org that contains, and compiles and installs all needed software to run a demonstrator in a single command. This is the recommended solution to get started.

Building

Depending on how the underlying Verificatum Core Routines library is compiled, native code may be used. You can check this using

    vcr-<VCR_VERSION>-info complete

where <VCR_VERSION> is the version of the VCR library. Type vcr- and then use tab to get the rest of the command to execute. In any case this library is a requirement to install VMN.

1. You need to install Open JDK 10 (or later) and M4.

2. Please use

    ./configure
    make
   

   to build the software.

3. If you want to use native code for modular exponentiations etc, then you must build VCR with native code enabled and install it in that way. You may inspect the complete version of VCR you are using with the following command, where <VCR_VERSION> is your version of VCR.

    vcr-<VCR_VERSION>-info complete
   

4. Optionally, you may run unit tests:

    make check
   

   This takes some time, since it verifies both basic functionality as well as run some of the subprotocols in a simulated environment and some of these tests necessarily use almost realistic data sizes.

Installing

WARNING! Please read the following instructions carefully. Failure to do so may result in a completely insecure installation.

1. Please use

    make install
   

   to install the software. You may need to be root or use sudo.

2. The tools in the library, e.g., vog, that require a source of randomness to function, uses the random source defined by two files that by default are named:

   $HOME/.verificatum_random_source
   $HOME/.verificatum_random_seed
   

   The first stores a description of a random device or a PRG and the second stores a random seed if a PRG is used.

   Here $HOME denotes the home directory of the user. The command vog is a script that invokes the java interpreter on the class com.verificatum.ui.gen.GeneratorTool.

   You may override the location of these files by setting the environment variables:

   VERIFICATUM_RANDOM_SOURCE
   VERIFICATUM_RANDOM_SEED
   

   WARNING!

   If an adversary is able to write to any of these files, then the software provides no security at all.

   If an adversary is able to read from the second file, then the software provides no security at all. The contents of the first file can safely be made public if it cannot be changed.

   If you use the environment variables, then you must make sure that nobody can modify them.

   Please understand that this software is meant to be run in a secure environment. You are responsible for providing this environment.

3. The above two files must be initialized using vog before any commands that require randomness are used. You can do this as follows.

   vog -rndinit RandomDevice <my device>
   Successfully initialized random source!
   

   If you wish to use a PRG instead, then you need to provide a seed as well, e.g., to use a provably secure PRG under the DDH assumption you could execute:

   vog -rndinit -seed seedfile PRGElGamal -fixed 1024
   Successfully initialized random source! Deleted seed file.
   

   The command replaces the seed file each time it is invoked to avoid accidental reuse.

   If you wish to change the random source you need to remove the files that store the random source and initialize it again with your new choice.

   WARNING!

   The provided seed file must contain bits that are indistinguishable from truly random bits. The seed bits must not be reused here or anywhere else.

   Failure to provide a proper seed file may result in a catastrophic privacy breach.

   If you decide to use fixed seed that you re-use for testing purposes, then please make sure to implement a mechanism that prevents you from accidentally using this in a real installation.

Usage

Comprehensive documentation ready for printing can be downloaded at https://www.verificatum.org, but you can also go directly to the demo/mixnet directory and run the ./demo script if you are impatient. demo/mixnet/README.md explains how to configure the demo.

You can also configure benchmark suites and run them remotely on multiple machines.

Technical information can, after installing, be found by using

    vtm -h

which gives an overview of the available commands. More usage information about each command can then be printed similarly.

API Documentation

You may use

    make api

to invoke Javadoc to build the API. The API is not installed anywhere. You can copy it to any location.

Reporting Bugs

Minor bugs should be reported in the repository system as issues or bugs. Security critical bugs, vulnerabilities, etc should be reported directly to Verificatum AB. We will make best effort to disclose the information in a responsible way before the finder gets proper credit.