pycrypt

A pure Python implementation of cryptographic primitives, written in a clean, Pythonic, and type-safe way.

Note

Disclaimer: pycrypt is an educational cryptography library. It is not safe for production use. Use only to learninge how cryptographic algorithms work under the hood. For production, use a vetted library such as cryptography.

API Reference

Overview

pycrypt implements major cryptographic primitives from scratch in pure Python with minimal dependencies. It is designed for learners and developers interested in the inner workings of cryptography.

Features

Category	Algorithm	Description
Asymmetric	RSA	OAEP encryption/decryption, PSS signing/verification
Asymmetric	Diffie–Hellman (DH)	Modular exponentiation and HKDF-based key derivation
Symmetric	AES	ECB, CBC, CTR, and GCM modes
Hashing	SHA-1, SHA-256	HMAC and HKDF included

Installation

pip install pycrypt-lib

Usage Examples

Diffie–Hellman (DH) Key Exchange

from pycrypt.asymmetric import DH

params = DH.generate_parameters(2048)

alice_priv = params.generate_private_key()
bob_priv = params.generate_private_key()

alice_shared = alice_priv.exchange(bob_priv.public_key())
bob_shared = bob_priv.exchange(alice_priv.public_key())

assert alice_shared == bob_shared
print(f"Shared secret: {alice_shared.hex()}")

RSA Encryption and Signing

from pycrypt.asymmetric import RSAKey

key = RSAKey.generate(2048)
message = b"Hello RSA!"

cipher = key.oaep_encrypt(message)
plain = key.oaep_decrypt(cipher)

signature = key.pss_sign(message)
assert key.pss_verify(message, signature)

AES Encryption (GCM Mode)

from secrets import token_bytes
from pycrypt.symmetric import AES_GCM

key = token_bytes(16)
nonce = token_bytes(12)

aes = AES_GCM(key)
ciphertext, tag = aes.encrypt(b"Top Secret", nonce=nonce)
plaintext = aes.decrypt(ciphertext, nonce=nonce, tag=tag)

print(plaintext.decode())

SHA-256 Hashing

from pycrypt.hash import SHA256

sha = SHA256()
sha.update(b"hello world")
print(sha.hexdigest())

License

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.