mykey

Warning: This crate is unaudited and experimental. It has not been professionally reviewed for security vulnerabilities, timing attacks, or logical flaws. Do not use it in production environments or to protect sensitive data.

A Rust implementation of MIKEY (Multimedia Internet KEYing, RFC 3830) for SRTP key exchange in AES67 and SMPTE ST 2110 environments.

Documentation & Book

Features

• Ephemeral Diffie-Hellman key exchange (X25519) — default
• Pre-shared key (PSK) mode with RFC 3830 §3.1 key transport — the TGK is randomly generated and AES-CM encrypted, and the message MAC is verified before decryption
• Optional verification messages (RFC 3830 §6.9) for mutual authentication
• SRTP key material derivation
• Security policy payload (RFC 3830 §6.10.1 — all SRTP parameters)
• SAP integration with a=key-mgmt:mikey SDP attribute (RFC 4567)
• Message parsing and serialization (wire format)
• Optional persistent identity keypairs with peer key pinning (MITM protection)

Interoperability

mykey is not a complete MIKEY implementation.

PSK mode — the only method RFC 3830 makes mandatory to implement — follows the spec for key transport (§3.1), key wrapping (§4.2.3), key data framing (§6.13), MAC computation (§5.2) and verification messages (§6.9). Two gaps remain: the timestamp is the optional COUNTER type rather than a mandatory NTP type, and there is no replay protection.

DH mode will not interoperate. It uses X25519 on a private-use DH-Group rather than an OAKLEY group, and omits the SIGN payload the RFC requires. This is deliberate — see the chapter below.

Every known departure is catalogued in Deviations from RFC 3830 — read it before assuming a mykey exchange will interoperate with another MIKEY stack.

Add to your project

[dependencies]
mykey = "2.0.0"

or to get whatever the latest in Crates.io is, just type:

cargo add mykey

Quick start

Ephemeral DH key exchange

use mykey::{DhInitiator, DhResponder, srtp::SrtpCryptoSuite};

let suite = SrtpCryptoSuite::AES_128_CM_SHA1_80;

// --- Initiator side ---
let initiator = DhInitiator::new(csc_id, ssrc);
let init_msg = initiator.init_message()?;

// Send init_msg.to_bytes() to the responder over the network / SDP

// --- Responder side ---
let responder = DhResponder::new();
let resp_msg = responder.resp_message(csc_id)?;

// Send resp_msg.to_bytes() back to the initiator

// Both sides derive the same SRTP keys
let keys = initiator.complete(&resp_msg, suite)?;

PSK mode

use mykey::message::MikeyMessage;

let psk = b"shared-secret-key";
let rand_bytes = [0x42u8; 16]; // use rand::rng() in practice
let msg = MikeyMessage::new_psk_init(csc_id, ssrc, &rand_bytes, psk)?;

SAP / SDP integration

use mykey::{DhInitiator, sap::{build_sap_with_mikey, mikey_to_sdp_attribute}};

let initiator = DhInitiator::new(1, 0xDEADBEEF);
let msg = initiator.init_message()?;

// RFC 4567: a=key-mgmt:mikey <base64>
let sdp_line = mikey_to_sdp_attribute(&msg);

// Or wrap in a full SAP packet (origin is the announcer's IPv4 address)
let sap = build_sap_with_mikey([192, 168, 1, 10], 0x1234, &sdp_body, &msg);

Peer key pinning (opt-in MITM protection)

use std::path::Path;
use mykey::identity::{Identity, PinnedPeer};

// Generate or load a persistent keypair
let my_id = Identity::load_or_generate(Path::new("/etc/mykey"))?;

// Load a peer's public key distributed out-of-band (rsync, scp, etc.)
let peer = PinnedPeer::from_file("studio-b", Path::new("/etc/mykey/peers/studio-b.pub"))?;

// After receiving a MIKEY message, verify the DH public matches the pin
peer.verify(received_msg.dh_public().unwrap())?;

Key exchange mode summary

Mode	MITM protection	Pre-shared material	Forward secrecy
Ephemeral DH (default)	No	None	Yes
PSK	Initiator only — the responder authenticates the initiator, not the reverse	Shared key	No
PSK + verification message	Yes, mutual (both sides prove they hold the key)	Shared key	No
Ephemeral DH + pinning	Yes (pinned public key)	Public key only	Yes

No mode currently provides replay protection — a captured message can be replayed and will be accepted. See Deviations from RFC 3830.

Dependencies

Crate	Purpose
x25519-dalek	X25519 DH key exchange
hmac + sha1	MIKEY-1 PRF and KEMAC MAC (HMAC-SHA-1, per RFC 3830)
aes + ctr	AES-CM key wrapping of the KEMAC payload (RFC 3830 §4.2.3)
base64	SDP a=key-mgmt:mikey encoding
hex	Identity key file encoding
rand ≥ 0.9 + rand_core	RAND nonce generation; OsRng (direct OS entropy) for X25519 keypairs. 0.9+ required to address RUSTSEC-2026-0097.
thiserror	Error types

License

Licensed under either of Apache License, Version 2.0 or MIT License at your option.