Jędrzej Stuczyński
56 lines
1.9 KiB
Rust
56 lines
1.9 KiB
Rust
// Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
|
|
// SPDX-License-Identifier: Apache-2.0
|
|
|
|
use crate::asymmetric::encryption;
|
|
use crate::hkdf;
|
|
use cipher::{Key, KeyIvInit, StreamCipher};
|
|
use digest::crypto_common::BlockSizeUser;
|
|
use digest::Digest;
|
|
#[cfg(feature = "rand")]
|
|
use rand::{CryptoRng, RngCore};
|
|
|
|
/// Generate an ephemeral encryption keypair and perform diffie-hellman to establish
|
|
/// shared key with the remote.
|
|
#[cfg(feature = "rand")]
|
|
pub fn new_ephemeral_shared_key<C, D, R>(
|
|
rng: &mut R,
|
|
remote_key: &encryption::PublicKey,
|
|
) -> (encryption::KeyPair, Key<C>)
|
|
where
|
|
C: StreamCipher + KeyIvInit,
|
|
D: Digest + BlockSizeUser + Clone,
|
|
R: RngCore + CryptoRng,
|
|
{
|
|
let ephemeral_keypair = encryption::KeyPair::new(rng);
|
|
|
|
// after performing diffie-hellman we don't care about the private component anymore
|
|
let dh_result = ephemeral_keypair.private_key().diffie_hellman(remote_key);
|
|
|
|
// there is no reason for this to fail as our okm is expected to be only C::KeySize bytes
|
|
let okm = hkdf::extract_then_expand::<D>(None, &dh_result, None, C::key_size())
|
|
.expect("somehow too long okm was provided");
|
|
|
|
let derived_shared_key =
|
|
Key::<C>::from_exact_iter(okm).expect("okm was expanded to incorrect length!");
|
|
|
|
(ephemeral_keypair, derived_shared_key)
|
|
}
|
|
|
|
/// Recompute shared key using remote public key and local private key.
|
|
pub fn recompute_shared_key<C, D>(
|
|
remote_key: &encryption::PublicKey,
|
|
local_key: &encryption::PrivateKey,
|
|
) -> Key<C>
|
|
where
|
|
C: StreamCipher + KeyIvInit,
|
|
D: Digest + BlockSizeUser + Clone,
|
|
{
|
|
let dh_result = local_key.diffie_hellman(remote_key);
|
|
|
|
// there is no reason for this to fail as our okm is expected to be only C::KeySize bytes
|
|
let okm = hkdf::extract_then_expand::<D>(None, &dh_result, None, C::key_size())
|
|
.expect("somehow too long okm was provided");
|
|
|
|
Key::<C>::from_exact_iter(okm).expect("okm was expanded to incorrect length!")
|
|
}
|