Go Basic Cryptography Algorithms

This repository contains implementations of basic cryptographic algorithms in Go, focusing on mathematical foundations and simple substitution or transformation techniques.
The goal is educational: understand how these algorithms work and practice implementing them from scratch.

Implemented Algorithms

The project includes the following basic cryptography algorithms:

1. Caesar Cipher

• Simple substitution cipher.
• Each letter (or byte) is shifted by a fixed key.
• Formula (byte-wise): C = P + k (wrap-around automatic in Go byte)
• Example: "HELLO" + key 3 → "KHOOR"

2. ROT-n / ROT13

• Special case of Caesar Cipher.
• Rotates letters by n positions (ROT13 rotates by 13).
• Can be applied to all letters or ASCII bytes.

3. Vigenère Cipher

• Polyalphabetic substitution cipher.
• Each character is shifted by the corresponding character in a repeated key.
• Byte-wise formula: C_i = message[i] + key[i % len(key)]
• Works on letters or all ASCII bytes.

4. Affine Cipher

• A mathematical cipher using a linear function over modulo 26 (or 256 for bytes).
• Encryption: C = (a*P + b) mod m
• Decryption: P = a_inv * (C - b) mod m
• Introduces multiplication for more complex substitutions.

5. Substitution Cipher (Random / Fixed Table)

• Each symbol is replaced with another according to a mapping table.
• Can be implemented with letters, numbers, or full ASCII.

6. XOR Cipher

• Simple symmetric cipher using bitwise XOR.
• C = P ⊕ K
• Very fast and can work on bytes, files, and strings.
• Can be extended to a repeating key (like Vigenère with XOR).

7. ROT by Bytes / Extended Caesar

• Applies the Caesar logic to all bytes of a message or file.
• Demonstrates wrap-around naturally in Go using byte.

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Project Goals

• Educational: understand basic cryptographic transformations.
• Mathematical foundation: show formulas and byte-level operations.
• Hands-on implementation: all algorithms coded in Go from scratch.
• Extendable: easy to add new simple ciphers in the future.

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