Cryptography 2017/2018 at MFI, University of Gdansk

1. Caesar & Affine (rotational cipher)

Prerequisites

• plain.txt - source text
• key.txt - key
• extra.txt - helper text for cryptoanalysis (part of source text)

Usage

• AffineCipher.exe -[a|c] -[e|d|k|j]
• arg1: a (affine mode), c (caesar mode)
• arg2: e (encrypt), d (decrypt), j (cryptoanalysis with helper text), k (brute force)

Remarks

• all characters except for english letters are ignored
• key has format Ax + B, A is ignored in caesar mode

2. OTP / One-Time-Password (xor cipher)

Prerequisites

• oring.txt - source text
• key.txt - key

Usage

• OTP.exe -[p|e|k]
• arg1: p (prepare text), e (encrypt), k (brute force)

Remarks

• line length = 16
• CR/LF is not taken into account

3. ECB & CBC (block cipher)

Prerequisites

• plain.bmp - image with 24 bits per pixel (bitmap-24)
• key.txt - key (binary number)

Usage

• Block.exe

Remarks

• block size is determined by BlockWidth and BlockHeight consts
• bitmap width = multiple of BlockWidth, height respectively
• key length has to be greater or equal to block size (BlockWidth * BlockHeight)
• default block size: 4x4 px, key = 16

4. Hash functions

Prerequisites

• hash.txt - file with computed hash-pairs

Usage

• diff.rb > diff.txt

Remarks

• hash pair contains 2 function calls followed by 2 computed hashes (4 successive lines)
• summary takes two args - entry line-start index and source file

5. Vigenere

Prerequisites

• oring.txt - source text
• key.txt - key

Usage

• Vigenere.exe -[p|e|d|k]
• arg1: p (prepare text), e (encrypt), d (decrypt), k (brute force)

Remarks

• only english texts are valid because of defined letter frequencies

6. ElGamal

Prerequisites

• plain.text - source text for encryption
• message.txt - source text for signature
• elgamal.txt - generator and prime number

Usage

• ElGamal.exe -[k|e|d|s|v]
• arg1: k (generate keys), e (encrypt), d (decrypt), s (sign), v (verify signature)

Remarks

• source text consists of a single number (interpreted as a number, not ASCII)