sihensel/blowfish

Temporary fork for the Implementation Attacks class

BLOWFISH ENCRYPTION ALGORITHM

Fork of https://github.com/prophet6250/blowfish-implementation.

Compile the code

gcc blowfish.c main.c -o ./blowfish -lm

Usage

./blowfish <arg> <plaintext>

<arg> can take the following parameters:

Arg	Description
encrypt	Performs a regular Blowfish encryption
sbox	Attack model when attacking round keys via sboxes
xor	Attack model when attacking round keys via XOR operations
feistel	Attack model when attacking the result of f()
print_feistel	Print the result of f() for a given input

<plaintext> consists of 8 input bytes in decimal form, delimited by a space, such as 1 2 3 4 5 6 7 8.

The encryption key is hardcoded in main.c.

Countermeasures

Countermeasures are implemented in the countermeasures directory, which contains a separate copy of the code. Here, the blowfish binary only takes <plaintext> as an argument and always performs a regular Blowfish encryption.

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ORIGINAL README BELOW

ABOUT

My Implementation of the 64-bit Blowfish Cryptographic block cipher

This is(never was) not meant to be used in production code, nor as a source of reference. This was purely a programming excercise. Mistakes & vulnerabilities are bound to creeep into this code. So don't use this code in professional environments.

REQUIREMENTS

My machine has GCC version 9.2.0. Although, any C compiler, with support of ISO C11 may be used to compile this code, preferably GCC version 4.9+

COMPILE AND RUN

gcc blowfish.c main.c -o ./blow -lm

./blow

HOW TO CHANGE PREDEFINED INPUTS

Inside main.c, there are two macro definitions, namely #define PLAINTEXT and #define KEY. Edit these values with your own custom plaintext and key values. Keep in mind, keysize should not be greater than 56 characters (preferable less than 55).

RESOURCES USED

1. https://morf.lv/introduction-to-data-encryption (basic feistel cipher and then Blowfish using Qt and C++)