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ECDH Encrypted Key Exchange (Python 3.6+)
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| from cryptography.hazmat.backends import default_backend | |
| from cryptography.hazmat.primitives import hashes, padding | |
| from cryptography.hazmat.primitives.asymmetric import ec | |
| from cryptography.hazmat.primitives.kdf.hkdf import HKDF | |
| from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes | |
| from secrets import token_bytes | |
| class DiffieHellman: | |
| def __init__(self): | |
| self.diffieHellman = ec.generate_private_key(ec.SECP384R1(), default_backend()) | |
| self.public_key = self.diffieHellman.public_key() | |
| self.IV = token_bytes(16) | |
| def encrypt(self, public_key, secret): | |
| shared_key = self.diffieHellman.exchange(ec.ECDH(), public_key) | |
| derived_key = HKDF( | |
| algorithm=hashes.SHA256(), | |
| length=32, | |
| salt=None, | |
| info=None, | |
| backend=default_backend() | |
| ).derive(shared_key) | |
| aes = Cipher(algorithms.AES(derived_key), modes.CBC(self.IV), backend=default_backend()) | |
| encryptor = aes.encryptor() | |
| padder = padding.PKCS7(128).padder() | |
| padded_data = padder.update(secret.encode()) + padder.finalize() | |
| return encryptor.update(padded_data) + encryptor.finalize() | |
| def decrypt(self, public_key, secret, iv): | |
| shared_key = self.diffieHellman.exchange(ec.ECDH(), public_key) | |
| derived_key = HKDF( | |
| algorithm=hashes.SHA256(), | |
| length=32, | |
| salt=None, | |
| info=None, | |
| backend=default_backend() | |
| ).derive(shared_key) | |
| aes = Cipher(algorithms.AES(derived_key), modes.CBC(iv), backend=default_backend()) | |
| decryptor = aes.decryptor() | |
| decrypted_data = decryptor.update(secret) + decryptor.finalize() | |
| unpadder = padding.PKCS7(128).unpadder() | |
| return unpadder.update(decrypted_data) + unpadder.finalize() | |
| text = "Hello World!" | |
| alice = DiffieHellman() | |
| bob = DiffieHellman() | |
| encrypted_message = bob.encrypt(alice.public_key, text) | |
| print(encrypted_message) | |
| decrypted_message = alice.decrypt(bob.public_key, encrypted_message, bob.IV) | |
| print(decrypted_message) |
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