272 lines
6.7 KiB
JavaScript
272 lines
6.7 KiB
JavaScript
var assert = require('assert')
|
|
var crypto = require('./crypto')
|
|
|
|
var BigInteger = require('bigi')
|
|
var ECPointFp = require('./ec').ECPointFp
|
|
|
|
function deterministicGenerateK(ecparams, hash, D) {
|
|
assert(Buffer.isBuffer(hash), 'Hash must be a Buffer, not ' + hash)
|
|
assert.equal(hash.length, 32, 'Hash must be 256 bit')
|
|
assert(D instanceof BigInteger, 'Private key must be a BigInteger')
|
|
|
|
var x = D.toBuffer(32)
|
|
var k = new Buffer(32)
|
|
var v = new Buffer(32)
|
|
k.fill(0)
|
|
v.fill(1)
|
|
|
|
k = crypto.HmacSHA256(Buffer.concat([v, new Buffer([0]), x, hash]), k)
|
|
v = crypto.HmacSHA256(v, k)
|
|
|
|
k = crypto.HmacSHA256(Buffer.concat([v, new Buffer([1]), x, hash]), k)
|
|
v = crypto.HmacSHA256(v, k)
|
|
v = crypto.HmacSHA256(v, k)
|
|
|
|
var n = ecparams.getN()
|
|
var kB = BigInteger.fromBuffer(v).mod(n)
|
|
assert(kB.compareTo(BigInteger.ONE) > 0, 'Invalid k value')
|
|
assert(kB.compareTo(ecparams.getN()) < 0, 'Invalid k value')
|
|
|
|
return kB
|
|
}
|
|
|
|
function sign(ecparams, hash, D) {
|
|
var k = deterministicGenerateK(ecparams, hash, D)
|
|
|
|
var n = ecparams.getN()
|
|
var G = ecparams.getG()
|
|
var Q = G.multiply(k)
|
|
var e = BigInteger.fromBuffer(hash)
|
|
|
|
var r = Q.getX().toBigInteger().mod(n)
|
|
assert.notEqual(r.signum(), 0, 'Invalid R value')
|
|
|
|
var s = k.modInverse(n).multiply(e.add(D.multiply(r))).mod(n)
|
|
assert.notEqual(s.signum(), 0, 'Invalid S value')
|
|
|
|
var N_OVER_TWO = n.shiftRight(1)
|
|
|
|
// enforce low S values, see bip62: 'low s values in signatures'
|
|
if (s.compareTo(N_OVER_TWO) > 0) {
|
|
s = n.subtract(s)
|
|
}
|
|
|
|
return {r: r, s: s}
|
|
}
|
|
|
|
function verify(ecparams, hash, r, s, Q) {
|
|
var e = BigInteger.fromBuffer(hash)
|
|
|
|
return verifyRaw(ecparams, e, r, s, Q)
|
|
}
|
|
|
|
function verifyRaw(ecparams, e, r, s, Q) {
|
|
var n = ecparams.getN()
|
|
var G = ecparams.getG()
|
|
|
|
if (r.compareTo(BigInteger.ONE) < 0 || r.compareTo(n) >= 0) {
|
|
return false
|
|
}
|
|
|
|
if (s.compareTo(BigInteger.ONE) < 0 || s.compareTo(n) >= 0) {
|
|
return false
|
|
}
|
|
|
|
var c = s.modInverse(n)
|
|
var u1 = e.multiply(c).mod(n)
|
|
var u2 = r.multiply(c).mod(n)
|
|
|
|
var point = G.multiplyTwo(u1, Q, u2)
|
|
var v = point.getX().toBigInteger().mod(n)
|
|
|
|
return v.equals(r)
|
|
}
|
|
|
|
/**
|
|
* Serialize a signature into DER format.
|
|
*
|
|
* Takes two BigIntegers representing r and s and returns a byte array.
|
|
*/
|
|
function serializeSig(r, s) {
|
|
var rBa = r.toDERInteger()
|
|
var sBa = s.toDERInteger()
|
|
|
|
var sequence = []
|
|
sequence.push(0x02); // INTEGER
|
|
sequence.push(rBa.length)
|
|
sequence = sequence.concat(rBa)
|
|
|
|
sequence.push(0x02); // INTEGER
|
|
sequence.push(sBa.length)
|
|
sequence = sequence.concat(sBa)
|
|
|
|
sequence.unshift(sequence.length)
|
|
sequence.unshift(0x30); // SEQUENCE
|
|
|
|
return sequence
|
|
}
|
|
|
|
/**
|
|
* Parses a buffer containing a DER-encoded signature.
|
|
*
|
|
* This function will return an object of the form:
|
|
*
|
|
* {
|
|
* r: BigInteger,
|
|
* s: BigInteger
|
|
* }
|
|
*/
|
|
function parseSig(buffer) {
|
|
assert.equal(buffer.readUInt8(0), 0x30, 'Not a DER sequence')
|
|
assert.equal(buffer.readUInt8(1), buffer.length - 2, 'Invalid sequence length')
|
|
|
|
assert.equal(buffer.readUInt8(2), 0x02, 'Expected DER integer')
|
|
var rLen = buffer.readUInt8(3)
|
|
var rB = buffer.slice(4, 4 + rLen)
|
|
|
|
var offset = 4 + rLen
|
|
assert.equal(buffer.readUInt8(offset), 0x02, 'Expected a 2nd DER integer')
|
|
var sLen = buffer.readUInt8(1 + offset)
|
|
var sB = buffer.slice(2 + offset)
|
|
|
|
return {
|
|
r: BigInteger.fromDERInteger(rB),
|
|
s: BigInteger.fromDERInteger(sB)
|
|
}
|
|
}
|
|
|
|
function serializeSigCompact(r, s, i, compressed) {
|
|
if (compressed) {
|
|
i += 4
|
|
}
|
|
|
|
i += 27
|
|
|
|
var buffer = new Buffer(65)
|
|
buffer.writeUInt8(i, 0)
|
|
r.toBuffer(32).copy(buffer, 1)
|
|
s.toBuffer(32).copy(buffer, 33)
|
|
|
|
return buffer
|
|
}
|
|
|
|
function parseSigCompact(buffer) {
|
|
assert.equal(buffer.length, 65, 'Invalid signature length')
|
|
var i = buffer.readUInt8(0) - 27
|
|
|
|
// At most 3 bits
|
|
assert.equal(i, i & 7, 'Invalid signature type')
|
|
var compressed = !!(i & 4)
|
|
|
|
// Recovery param only
|
|
i = i & 3
|
|
|
|
var r = BigInteger.fromBuffer(buffer.slice(1, 33))
|
|
var s = BigInteger.fromBuffer(buffer.slice(33))
|
|
|
|
return {
|
|
r: r,
|
|
s: s,
|
|
i: i,
|
|
compressed: compressed
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Recover a public key from a signature.
|
|
*
|
|
* See SEC 1: Elliptic Curve Cryptography, section 4.1.6, "Public
|
|
* Key Recovery Operation".
|
|
*
|
|
* http://www.secg.org/download/aid-780/sec1-v2.pdf
|
|
*/
|
|
function recoverPubKey(ecparams, e, r, s, i) {
|
|
assert.strictEqual(i & 3, i, 'The recovery param is more than two bits')
|
|
|
|
// A set LSB signifies that the y-coordinate is odd
|
|
// By reduction, the y-coordinate is even if it is clear
|
|
var isYEven = !(i & 1)
|
|
|
|
// The more significant bit specifies whether we should use the
|
|
// first or second candidate key.
|
|
var isSecondKey = i >> 1
|
|
|
|
var n = ecparams.getN()
|
|
var G = ecparams.getG()
|
|
var curve = ecparams.getCurve()
|
|
var p = curve.getQ()
|
|
var a = curve.getA().toBigInteger()
|
|
var b = curve.getB().toBigInteger()
|
|
|
|
// We precalculate (p + 1) / 4 where p is the field order
|
|
if (!curve.P_OVER_FOUR) {
|
|
curve.P_OVER_FOUR = p.add(BigInteger.ONE).shiftRight(2)
|
|
}
|
|
|
|
// 1.1 Compute x
|
|
var x = isSecondKey ? r.add(n) : r
|
|
|
|
// 1.3 Convert x to point
|
|
var alpha = x.pow(3).add(a.multiply(x)).add(b).mod(p)
|
|
var beta = alpha.modPow(curve.P_OVER_FOUR, p)
|
|
|
|
// If beta is even, but y isn't, or vice versa, then convert it,
|
|
// otherwise we're done and y == beta.
|
|
var y = (beta.isEven() ^ isYEven) ? p.subtract(beta) : beta
|
|
|
|
// 1.4 Check that nR isn't at infinity
|
|
var R = new ECPointFp(curve, curve.fromBigInteger(x), curve.fromBigInteger(y))
|
|
R.validate()
|
|
|
|
// 1.5 Compute -e from e
|
|
var eNeg = e.negate().mod(n)
|
|
|
|
// 1.6 Compute Q = r^-1 (sR - eG)
|
|
// Q = r^-1 (sR + -eG)
|
|
var rInv = r.modInverse(n)
|
|
|
|
var Q = R.multiplyTwo(s, G, eNeg).multiply(rInv)
|
|
Q.validate()
|
|
|
|
if (!verifyRaw(ecparams, e, r, s, Q)) {
|
|
throw new Error("Pubkey recovery unsuccessful")
|
|
}
|
|
|
|
return Q
|
|
}
|
|
|
|
/**
|
|
* Calculate pubkey extraction parameter.
|
|
*
|
|
* When extracting a pubkey from a signature, we have to
|
|
* distinguish four different cases. Rather than putting this
|
|
* burden on the verifier, Bitcoin includes a 2-bit value with the
|
|
* signature.
|
|
*
|
|
* This function simply tries all four cases and returns the value
|
|
* that resulted in a successful pubkey recovery.
|
|
*/
|
|
function calcPubKeyRecoveryParam(ecparams, e, r, s, Q) {
|
|
for (var i = 0; i < 4; i++) {
|
|
var Qprime = recoverPubKey(ecparams, e, r, s, i)
|
|
|
|
if (Qprime.equals(Q)) {
|
|
return i
|
|
}
|
|
}
|
|
|
|
throw new Error('Unable to find valid recovery factor')
|
|
}
|
|
|
|
module.exports = {
|
|
calcPubKeyRecoveryParam: calcPubKeyRecoveryParam,
|
|
deterministicGenerateK: deterministicGenerateK,
|
|
recoverPubKey: recoverPubKey,
|
|
sign: sign,
|
|
verify: verify,
|
|
verifyRaw: verifyRaw,
|
|
serializeSig: serializeSig,
|
|
parseSig: parseSig,
|
|
serializeSigCompact: serializeSigCompact,
|
|
parseSigCompact: parseSigCompact
|
|
}
|