*   *      __        __  ___  ____   _____  _  __ __  __
   \ /       \ \      / / |_ _||  _ \ | ____|| |/ / \ \/ /
 ^/ | \^      \ \ /\ / /   | | | |_) ||  _|  | ' /   \  /
 | o:1 |       \ V  V /    | | |  _ < | |___ | . \   /  \
-| 1:o |-       \_/\_/    |___||_| \_\|_____||_|\_\ /_/\_\
/ \_|_/ \

Python library and wire format for anonymous X25519 key exchange.

wirekx v1 performs the following:

• Opportunistic key agreement for anonymous handshake

V1 caveat: Since this is an anonymous handshake, MITM is undetectable.

Use cases:

• Derive symmetric key for payload encryption between trusted services

Future releases:

• publicCA validation for anonymous handshake
• Pre-shared fingerprint validation
• Quantum-safe encryption

Install for development

python3 -m venv .venv
.venv/bin/python -m pip install -e ".[dev]"

Run the manual example:

.venv/bin/python testrun.py

Run tests:

.venv/bin/python -m pytest

Use as a library:

from wirekx import InitiatorHandshake, ResponderHandshake

initiator = InitiatorHandshake()
responder = ResponderHandshake()

hello = initiator.create_hello()
responder.receive_hello(hello)

hello_back = responder.create_hello_back()
initiator.receive_hello_back(hello_back)

initiator_confirm = initiator.create_confirm()
responder.receive_confirm(initiator_confirm)

responder_confirm = responder.create_confirm()
initiator.receive_confirm(responder_confirm)

result = initiator.result()
print(result.symmetric_key.hex())

Open source contribution flow

1. Fork the repository on GitHub.
2. Create a branch for your change.
3. Install development dependencies with .venv/bin/python -m pip install -e ".[dev]".
4. Add or update tests in tests/.
5. Run .venv/bin/python -m pytest.
6. Open a pull request.

License

wirekx is licensed under the Apache License, Version 2.0. See LICENSE.

Redistributions should preserve the attribution notices in NOTICE. If you use wirekx in a public project, a README or documentation mention is appreciated.

wirekx wire format (v1, anonymous mode)

Two parties run a handshake and end up holding the same 32-byte symmetric key. This document specifies the bytes that go on the wire.

Envelope

Every message starts with a 4-byte header followed by its payload.

┌─────────┬──────────┬─────────────┬──────────────┐
│ version │ msg_type │ payload_len │   payload    │
│ 1 byte  │  1 byte  │  2 bytes BE │ payload_len  │
└─────────┴──────────┴─────────────┴──────────────┘

version = 0x01. Multi-byte integers are big-endian.

Messages

Code	Name	From	Payload
0x01	HELLO	initiator	eph_pub_a (32) + nonce_a (32)
0x02	HELLO_BACK	responder	eph_pub_b (32) + nonce_b (32)
0x03	CONFIRM	both	verify_data (32)

eph_pub_* is an X25519 public key. nonce_* is 32 random bytes.

Cryptography

shared_secret  = X25519(own_eph_priv, peer_eph_pub)

symmetric_key  = HKDF-SHA256(
    ikm    = shared_secret,
    salt   = nonce_a || nonce_b,
    info   = "wirekx v1 session key",
    length = 32)

transcript     = SHA-256(HELLO_bytes || HELLO_BACK_bytes)

verify_data    = HMAC-SHA256(
    key  = symmetric_key,
    data = "wirekx v1 <role> confirm" || transcript)

<role> is initiator or responder depending on who sent the CONFIRM. Compare received verify_data with constant-time equality. Mismatch = abort.

Flow

initiator                              responder
    │                                       │
    │   HELLO  (eph_pub_a, nonce_a)         │
    │ ────────────────────────────────────► │
    │                                       │
    │   HELLO_BACK  (eph_pub_b, nonce_b)    │
    │ ◄──────────────────────────────────── │
    │                                       │
    │   derive symmetric_key, transcript    │
    │   CONFIRM  (verify_data_initiator)    │
    │ ────────────────────────────────────► │
    │                                       │
    │                                       │   verify, then:
    │   CONFIRM  (verify_data_responder)    │
    │ ◄──────────────────────────────────── │
    │                                       │
    │   verify                              │
    │   COMPLETE                            │   COMPLETE

On any malformed message, unexpected type, or verification mismatch: abort, discard state, do not return the key.

Output

After both CONFIRM messages verify, return to the caller:

• symmetric_key — 32 bytes
• transcript_hash — 32 bytes
• protection_level = "opportunistic"
• peer_identity = null

Notes

• transcript_hash is unique per handshake.
• Possible values for protection_level are "opportunistic" and "authenticated". Opportunistic means anonymous players, active MITM is undetectable. Authenticated means you have verified peer's identity by exchanging certificate via an external channel.
• Ephemeral keys are fresh per handshake and discarded after use.
• No version negotiation. Different versions cannot interoperate.
• Authenticated modes (fingerprint, shared, publicCA) will be built in future.