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README.md

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crypto-playground (from-scratch edition)

Educational repository implementing cryptographic primitives from scratch in pure Python — no crypto libraries. Everything includes step-by-step comments and docstrings.

⚠️ For learning only. Implementations are intentionally simple and not constant-time. Do not use for real security.

Contents

• Classical: Caesar, Vigenère, frequency analysis, Vigenère cracker.
• Modern (from scratch):
  • SHA-256, HMAC-SHA256, PBKDF2-HMAC-SHA256
  • AES-128 (key schedule, S-box, ECB/CTR), AEAD via Encrypt-then-MAC (AES-CTR + HMAC)
  • RSA (keygen with Miller–Rabin, OAEP encryption, PSS signatures)
  • Diffie–Hellman (integer group) & simplified TLS-style handshake demo
• Streamlit app to interact with all modules (uses only our code).

Quickstart

python -m venv .venv && source .venv/bin/activate  # Windows: .venv\Scripts\activate
pip install -r requirements.txt

# Run the web playground
streamlit run app.py

# Run tests
pytest -q

License

MIT — see LICENSE.