Implement cryptographic algorithms

Create implementations for basic cryptographic algorithms:

## Symmetric encryption:
- Caesar cipher
- Vigenère cipher
- One-time pad
- Substitution cipher
- Transposition cipher
- Rail fence cipher

## Hashing algorithms:
- Simple hash functions
- Rolling hash
- Merkle–Damgård construction

## Cryptographic primitives:
- Pseudo-random number generators
- Key derivation functions
- Message authentication codes

## Requirements:
- Include detailed mathematical explanations
- Provide security analysis
- Create comprehensive test cases
- Document practical applications

**Note:** These implementations are for educational purposes only. They demonstrate the principles behind cryptographic algorithms but should not be used for actual security-sensitive applications.

This collection will provide insight into the mathematical foundations of cryptography through simple, understandable implementations.