A basic implementation of 5 encryption algorithms, with a demo. Developed in the spring of 2022, as an assignment for my Introduction to Information Security Systems course.

• One Time Pad
• Rail Fence cipher
• Beaufort cipher
• Affine cipher
• Feistel cipher

Each cipher has a demo function which encrypts and decrypts a plaintext using the appropriate functions.

The OTP demo demonstrates the dangers of reusing the pad. Given 2 words encrypted with the same key and a wordlist, the demo successfully cracks the pad and prints the plaintexts. The given cyphertexts are:

• [0xe9 0x3a 0xe9 0xc5 0xfc 0x73 0x55 0xd5] ("networks")
• [0xf4 0x3a 0xfe 0xc7 0xe1 0x68 0x4a 0xdf] ("security")

To enable this behaviour, use the -c option.

cd cryptolib
make

./demo [-c]

make clean