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| import os | |
| import hashlib | |
| import binascii | |
| def kyber_keygen(): | |
| """ | |
| Simulated key generation for Kyber-512. | |
| Returns a tuple (public_key, secret_key) as hex strings. | |
| (In a real implementation, these would be generated via lattice-based algorithms.) | |
| """ | |
| public_key = os.urandom(32) # simulate 256-bit public key | |
| secret_key = os.urandom(32) # simulate 256-bit secret key | |
| return binascii.hexlify(public_key).decode(), binascii.hexlify(secret_key).decode() | |
| def kyber_encapsulate(public_key_hex): | |
| """ | |
| Simulated encapsulation for Kyber-512. | |
| Given a public key (as hex), returns a tuple (ciphertext, shared_secret) as hex strings. | |
| In a real KEM, the ciphertext encapsulates the shared secret. | |
| Here we simulate by hashing the public key with random bytes. | |
| """ | |
| public_key = binascii.unhexlify(public_key_hex) | |
| randomness = os.urandom(32) | |
| shared_secret = hashlib.sha256(public_key + randomness).digest() | |
| ciphertext = os.urandom(64) # simulated ciphertext | |
| return binascii.hexlify(ciphertext).decode(), binascii.hexlify(shared_secret).decode() | |
| def kyber_decapsulate(ciphertext_hex, secret_key_hex): | |
| """ | |
| Simulated decapsulation for Kyber-512. | |
| In a real KEM, this would recover the shared secret from the ciphertext using the secret key. | |
| Here we simulate by hashing the secret key with the ciphertext. | |
| """ | |
| ciphertext = binascii.unhexlify(ciphertext_hex) | |
| secret_key = binascii.unhexlify(secret_key_hex) | |
| shared_secret = hashlib.sha256(secret_key + ciphertext).digest() | |
| return binascii.hexlify(shared_secret).decode() | |
| def encrypt_message(message: str, key_hex: str): | |
| """ | |
| Simulated symmetric encryption using XOR with the shared secret. | |
| (This is NOT secure encryption; it's for demonstration only.) | |
| """ | |
| key = binascii.unhexlify(key_hex) | |
| message_bytes = message.encode() | |
| # Repeat the key to match the message length. | |
| repeated_key = (key * ((len(message_bytes) // len(key)) + 1))[:len(message_bytes)] | |
| ciphertext = bytes([mb ^ rb for mb, rb in zip(message_bytes, repeated_key)]) | |
| return binascii.hexlify(ciphertext).decode() | |
| def decrypt_message(ciphertext_hex: str, key_hex: str): | |
| """ | |
| Simulated symmetric decryption (reversing the XOR encryption). | |
| """ | |
| key = binascii.unhexlify(key_hex) | |
| ciphertext = binascii.unhexlify(ciphertext_hex) | |
| repeated_key = (key * ((len(ciphertext) // len(key)) + 1))[:len(ciphertext)] | |
| message_bytes = bytes([cb ^ rb for cb, rb in zip(ciphertext, repeated_key)]) | |
| return message_bytes.decode() | |
| if __name__ == "__main__": | |
| print("Kyber-512 Simulation Demo") | |
| pub_key, sec_key = kyber_keygen() | |
| print("Public Key:", pub_key) | |
| print("Secret Key:", sec_key) | |
| ct, shared_enc = kyber_encapsulate(pub_key) | |
| print("Ciphertext (encapsulation):", ct) | |
| print("Shared Secret (Encapsulation):", shared_enc) | |
| # For demonstration, simulate decapsulation (note: this simulation is not consistent with encapsulation) | |
| shared_dec = kyber_decapsulate(ct, sec_key) | |
| print("Shared Secret (Decapsulation):", shared_dec) | |
| message = "Hello Quantum World!" | |
| encrypted_msg = encrypt_message(message, shared_enc) | |
| print("Encrypted Message:", encrypted_msg) | |
| decrypted_msg = decrypt_message(encrypted_msg, shared_enc) | |
| print("Decrypted Message:", decrypted_msg) |