jakubriegel / geffe-generator

Functional style implemented Geffe cryptographic stream generator

Geffe Generator

about

Implementation of Geffe Generator using functional style Scala and lazy collections. Application provides command line and graphical interfaces.

Features:

• generation of geffe stream
• implementation of statistical tests: long series, poker and monobit
• two types of LFSR: xor and custom Fibonacci
• random registers generation

build

sbt
sbt:geffe> assembly

Generated jar will be available at target/scala-2.13/geffe.jar

cli

CLI was developed only for development purposes and has very limited features

generate stream

Type: java -jar geffe.jar stream <NUMBER_BITS_TO_GENERATE> <FIRST_LFSR_TYPE> <FIRST_LFSR_SIZE> <SECOND_LFSR_TYPE> <SECOND_LFSR_SIZE> <THIRD_LFSR_TYPE> <THIRD_LFSR_SIZE> CLI uses random registers of given size and type

Example: java -jar geffe.jar stream 100 xor 25 xor 25 fib 25

run FIPS tests

Type: java -jar geffe.jar test <FILE_WITH_STREAM_TO_TEST> Stream file should consist of 1s and 0s. The application will run 4 FIPS tests.

Example: java -jar geffe.jar test stream.txt

algorithm

how it works?

Geffe Generator uses three LFSRs connected non-linearly by multiplexer. General equation for this stream is:

k = (a3 AND a1) OR ((NOT a1) AND a2)

example

Using three 4-bit XOR registers:

• first with coefficients 0110 and initial state 1010
• second with coefficients 1101 and initial state 1111
• third with coefficients 1111 and initial state 0101

Generating 3-bit stream:

First bit:
    LFSR1:
        output: 1
        next state: 0101
    LFSR2:
        output: 1
        next state: 1111
    LFSR3:
        output: 0
        next state: 1010
    
    Bit: 0

Second bit:
    LFSR1:
        output: 1
        next state: 1011
    LFSR2:
        output: 1
        next state: 1111
    LFSR3:
        output: 1
        next state: 0101
    
    Bit: 1

Third bit:
    LFSR1:
        output: 1
        next state: 0111
    LFSR2:
        output: 1
        next state: 1111
    LFSR3:
        output: 0
        next state: 1010
    
    Bit: 0


Result: 010

credits

This is a project for Data Protection Basics course at Poznan University of Technology.