Module k256::ecdh

This is supported on crate feature ecdh only.

Elliptic Curve Diffie-Hellman (Ephemeral) Support.

This module contains a high-level interface for performing ephemeral Diffie-Hellman key exchanges using the secp256k1 elliptic curve.

Usage

This usage example is from the perspective of two participants in the exchange, nicknamed “Alice” and “Bob”.

use k256::{EncodedPoint, PublicKey, ecdh::EphemeralSecret};
use rand_core::OsRng; // requires 'getrandom' feature

// Alice
let alice_secret = EphemeralSecret::random(&mut OsRng);
let alice_pk_bytes = EncodedPoint::from(alice_secret.public_key());

// Bob
let bob_secret = EphemeralSecret::random(&mut OsRng);
let bob_pk_bytes = EncodedPoint::from(bob_secret.public_key());

// Alice decodes Bob's serialized public key and computes a shared secret from it
let bob_public = PublicKey::from_sec1_bytes(bob_pk_bytes.as_ref())
    .expect("bob's public key is invalid!"); // In real usage, don't panic, handle this!

let alice_shared = alice_secret.diffie_hellman(&bob_public);

// Bob deocdes Alice's serialized public key and computes the same shared secret
let alice_public = PublicKey::from_sec1_bytes(alice_pk_bytes.as_ref())
    .expect("alice's public key is invalid!"); // In real usage, don't panic, handle this!

let bob_shared = bob_secret.diffie_hellman(&alice_public);

// Both participants arrive on the same shared secret
assert_eq!(alice_shared.as_bytes(), bob_shared.as_bytes());

Type Definitions

EphemeralSecret	NIST P-256 Ephemeral Diffie-Hellman Secret.
SharedSecret	Shared secret value computed via ECDH key agreement.