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Use tweetnacl's X25519 implementation

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This commit is contained in:
Daniel Huigens 2019-05-01 07:56:39 +02:00
parent be1b4df140
commit ca0322bbea
1 changed files with 24 additions and 0 deletions
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24
src/crypto/public_key/elliptic/ecdh.js
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@ -18,6 +18,7 @@
/**
* @fileoverview Key encryption and decryption for RFC 6637 ECDH
* @requires bn.js
* @requires tweetnacl
* @requires crypto/public_key/elliptic/curve
* @requires crypto/aes_kw
* @requires crypto/cipher
@ -29,6 +30,7 @@
*/
import BN from 'bn.js';
import nacl from 'tweetnacl';
import Curve from './curves';
import aes_kw from '../../aes_kw';
import cipher from '../../cipher';
@ -85,6 +87,19 @@ async function kdf(hash_algo, S, length, param, curve, stripLeading=false, strip
* @async
*/
async function genPublicEphemeralKey(curve, Q) {
if (curve.name === 'curve25519') {
const { secretKey } = nacl.box.keyPair();
const one = curve.curve.curve.one;
const mask = one.ushln(255 - 3).sub(one).ushln(3);
let priv = new BN(secretKey);
priv = priv.or(one.ushln(255 - 1));
priv = priv.and(mask);
priv = priv.toArrayLike(Uint8Array, 'le', 32);
const S = nacl.scalarMult(priv, Q.subarray(1));
const { publicKey } = nacl.box.keyPair.fromSecretKey(priv);
const ret = { V: util.concatUint8Array([new Uint8Array([0x40]), publicKey]), S: new BN(S, 'le') };
return ret;
}
const v = await curve.genKeyPair();
Q = curve.keyFromPublic(Q);
const V = new Uint8Array(v.getPublic());
@ -124,6 +139,15 @@ async function encrypt(oid, cipher_algo, hash_algo, m, Q, fingerprint) {
* @async
*/
async function genPrivateEphemeralKey(curve, V, d) {
if (curve.name === 'curve25519') {
const one = curve.curve.curve.one;
const mask = one.ushln(255 - 3).sub(one).ushln(3);
let priv = new BN(d);
priv = priv.or(one.ushln(255 - 1));
priv = priv.and(mask);
const S = nacl.scalarMult(priv.toArrayLike(Uint8Array, 'le', 32), V.subarray(1));
return new BN(S, 'le');
}
V = curve.keyFromPublic(V);
d = curve.keyFromPrivate(d);
return d.derive(V);