109 lines
No EOL
3.4 KiB
Python
109 lines
No EOL
3.4 KiB
Python
import time
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from dataclasses import dataclass
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from Crypto.Hash import SHA256
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from Crypto.Protocol.KDF import HKDF
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from Crypto.Util import number
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def rfc3526_group14() -> tuple[int, int]:
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"""
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Return the 2048-bit MODP Group (Group 14) parameters from RFC 3526.
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g = 2
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p is the safe prime specified in RFC 3526, section 3.
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"""
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# RFC 3526 Group 14 (2048-bit MODP) prime (hex, concatenated)
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p_hex = (
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"FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1"
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"29024E088A67CC74020BBEA63B139B22514A08798E3404DD"
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"EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245"
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"E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED"
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"EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3D"
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"C2007CB8A163BF0598DA48361C55D39A69163FA8FD24CF5F"
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"83655D23DCA3AD961C62F356208552BB9ED529077096966D"
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"670C354E4ABC9804F1746C08CA18217C32905E462E36CE3B"
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"E39E772C180E86039B2783A2EC07A28FB5C55DF06F4C52C9"
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"DE2BCBF6955817183995497CEA956AE515D2261898FA0510"
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"15728E5A8AACAA68FFFFFFFFFFFFFFFF"
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)
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p = int(p_hex, 16)
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g = 2
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return p, g
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def int_to_fixed_length_bytes(value: int, length_bits: int) -> bytes:
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length_bytes = (length_bits + 7) // 8
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return value.to_bytes(length_bytes, byteorder="big")
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def generate_keypair(p: int, g: int, private_bits: int = 256) -> tuple[int, int]:
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a = 0
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while a < 2:
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a = number.getRandomNBitInteger(private_bits)
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A = pow(g, a, p)
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return a, A
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def derive_shared_key(peer_public: int, private: int, p: int, key_len: int = 32) -> bytes:
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shared_secret = pow(peer_public, private, p)
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# Use fixed-length big-endian encoding of the shared secret for KDF input
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shared_bytes = int_to_fixed_length_bytes(shared_secret, p.bit_length())
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key = HKDF(shared_bytes, key_len, salt=None, hashmod=SHA256, context=b"DH key")
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return key
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class TimingResult:
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alice_keygen_s: float
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bob_keygen_s: float
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alice_exchange_s: float
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bob_exchange_s: float
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def measure_timings(p: int, g: int, private_bits: int = 256) -> TimingResult:
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start = time.perf_counter()
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a_priv, a_pub = generate_keypair(p, g, private_bits)
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alice_keygen_s = time.perf_counter() - start
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start = time.perf_counter()
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b_priv, b_pub = generate_keypair(p, g, private_bits)
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bob_keygen_s = time.perf_counter() - start
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# Exchange
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start = time.perf_counter()
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a_key = derive_shared_key(b_pub, a_priv, p)
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alice_exchange_s = time.perf_counter() - start
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start = time.perf_counter()
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b_key = derive_shared_key(a_pub, b_priv, p)
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bob_exchange_s = time.perf_counter() - start
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# Sanity check
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if a_key != b_key:
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raise RuntimeError("Derived keys do not match. Check parameters.")
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return TimingResult(
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alice_keygen_s=alice_keygen_s,
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bob_keygen_s=bob_keygen_s,
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alice_exchange_s=alice_exchange_s,
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bob_exchange_s=bob_exchange_s,
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)
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def main():
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p, g = rfc3526_group14()
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timings = measure_timings(p, g, private_bits=256)
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print("Diffie-Hellman (RFC3526 Group 14, g=2)")
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print(f"Prime bits: {p.bit_length()}\n")
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print("Timings (seconds):")
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print(f"- Alice key generation: {timings.alice_keygen_s:.6f}")
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print(f"- Bob key generation: {timings.bob_keygen_s:.6f}")
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print(f"- Alice key exchange: {timings.alice_exchange_s:.6f}")
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print(f"- Bob key exchange: {timings.bob_exchange_s:.6f}")
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if __name__ == "__main__":
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main() |