BVernam: Binary Vernam

This is the solution of a project for the lecture of System Programming Lab at Bachelor Degree in Computer Science at University of Camerino. The goal of this project is to implement an adaptation of the Vernam's Cypher. This cypher is a one-time-pad based on a simble property of XOR binary operator:

(a XOR b) XOR b = c.

Given a sequence of k-bytes b₀b₁...b_k-1, the key, the encoding of any sequence s composed of N bytes d₀d₁...d_N-1 is obtained by splitting the sequence in K=ceil(N/k) blocks of the form D_j=d^j₀...d^j_kj. Each block is encoded by applying a one-time-pad and transformed in E_j=e^j₀...e^j_kj where:

e^j_i=b_{(j+i) mod k} XOR d^j_i

The output sequence is obtained as E₀...E_ceil(N/k).

Building

To build the project first of all you have to clone the repository from GitHub:

git clone https://github.com/michele-loreti/bvernam.git

This will dowload all the project source files in the folder bvernam.

After that one can use CMake to generate a Makefile:

cd bvernam cmake ./ make all

Executing

The program bvernam takes as input:

1. the file that is use as key;
2. the file to encode;
3. and the where the encoded sequence is stored.

To run program open a console and execute:

bvernam <keyfile> <inputfile> <outputfile>

Tests

A python script is available to test the program on different examples. The script, named runtests.py, can be found in the folder python_tests.

To run the test the following command can be used:

python3 ./python_tests/runtests.py