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var BN = require('bn.js');
var MillerRabin = require('miller-rabin');
var millerRabin = new MillerRabin();
var TWENTYFOUR = new BN(24);
var ELEVEN = new BN(11);
var TEN = new BN(10);
var THREE = new BN(3);
var SEVEN = new BN(7);
var primes = require('./generatePrime');
var randomBytes = require('randombytes');
module.exports = DH;
function setPublicKey(pub, enc) {
enc = enc || 'utf8';
if (!Buffer.isBuffer(pub)) {
pub = new Buffer(pub, enc);
}
this._pub = new BN(pub);
return this;
}
function setPrivateKey(priv, enc) {
enc = enc || 'utf8';
if (!Buffer.isBuffer(priv)) {
priv = new Buffer(priv, enc);
}
this._priv = new BN(priv);
return this;
}
var primeCache = {};
function checkPrime(prime, generator) {
var gen = generator.toString('hex');
var hex = [gen, prime.toString(16)].join('_');
if (hex in primeCache) {
return primeCache[hex];
}
var error = 0;
if (prime.isEven() ||
!primes.simpleSieve ||
!primes.fermatTest(prime) ||
!millerRabin.test(prime)) {
//not a prime so +1
error += 1;
if (gen === '02' || gen === '05') {
// we'd be able to check the generator
// it would fail so +8
error += 8;
} else {
//we wouldn't be able to test the generator
// so +4
error += 4;
}
primeCache[hex] = error;
return error;
}
if (!millerRabin.test(prime.shrn(1))) {
//not a safe prime
error += 2;
}
var rem;
switch (gen) {
case '02':
if (prime.mod(TWENTYFOUR).cmp(ELEVEN)) {
// unsuidable generator
error += 8;
}
break;
case '05':
rem = prime.mod(TEN);
if (rem.cmp(THREE) && rem.cmp(SEVEN)) {
// prime mod 10 needs to equal 3 or 7
error += 8;
}
break;
default:
error += 4;
}
primeCache[hex] = error;
return error;
}
function DH(prime, generator, malleable) {
this.setGenerator(generator);
this.__prime = new BN(prime);
this._prime = BN.mont(this.__prime);
this._primeLen = prime.length;
this._pub = undefined;
this._priv = undefined;
this._primeCode = undefined;
if (malleable) {
this.setPublicKey = setPublicKey;
this.setPrivateKey = setPrivateKey;
} else {
this._primeCode = 8;
}
}
Object.defineProperty(DH.prototype, 'verifyError', {
enumerable: true,
get: function () {
if (typeof this._primeCode !== 'number') {
this._primeCode = checkPrime(this.__prime, this.__gen);
}
return this._primeCode;
}
});
DH.prototype.generateKeys = function () {
if (!this._priv) {
this._priv = new BN(randomBytes(this._primeLen));
}
this._pub = this._gen.toRed(this._prime).redPow(this._priv).fromRed();
return this.getPublicKey();
};
DH.prototype.computeSecret = function (other) {
other = new BN(other);
other = other.toRed(this._prime);
var secret = other.redPow(this._priv).fromRed();
var out = new Buffer(secret.toArray());
var prime = this.getPrime();
if (out.length < prime.length) {
var front = new Buffer(prime.length - out.length);
front.fill(0);
out = Buffer.concat([front, out]);
}
return out;
};
DH.prototype.getPublicKey = function getPublicKey(enc) {
return formatReturnValue(this._pub, enc);
};
DH.prototype.getPrivateKey = function getPrivateKey(enc) {
return formatReturnValue(this._priv, enc);
};
DH.prototype.getPrime = function (enc) {
return formatReturnValue(this.__prime, enc);
};
DH.prototype.getGenerator = function (enc) {
return formatReturnValue(this._gen, enc);
};
DH.prototype.setGenerator = function (gen, enc) {
enc = enc || 'utf8';
if (!Buffer.isBuffer(gen)) {
gen = new Buffer(gen, enc);
}
this.__gen = gen;
this._gen = new BN(gen);
return this;
};
function formatReturnValue(bn, enc) {
var buf = new Buffer(bn.toArray());
if (!enc) {
return buf;
} else {
return buf.toString(enc);
}
}
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