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ecdsa: use shamirs trick

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This commit is contained in:
Daniel Cousens 2014-05-10 15:24:49 +10:00
parent e4aac0f2de
commit abe65b8d4a
1 changed files with 3 additions and 34 deletions
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37
src/ecdsa.js
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@ -6,32 +6,6 @@ var ecparams = sec("secp256k1")
var BigInteger = require('bigi')
var ECPointFp = require('./ec').ECPointFp
function implShamirsTrick(P, k, Q, l) {
var m = Math.max(k.bitLength(), l.bitLength())
var Z = P.add2D(Q)
var R = P.curve.getInfinity()
for (var i = m - 1; i >= 0; --i) {
R = R.twice2D()
R.z = BigInteger.ONE
if (k.testBit(i)) {
if (l.testBit(i)) {
R = R.add2D(Z)
} else {
R = R.add2D(P)
}
} else {
if (l.testBit(i)) {
R = R.add2D(Q)
}
}
}
return R
}
var ecdsa = {
deterministicGenerateK: function(hash, D) {
assert(Buffer.isBuffer(hash), 'Hash must be a Buffer')
@ -125,12 +99,7 @@ var ecdsa = {
var u1 = e.multiply(c).mod(n)
var u2 = r.multiply(c).mod(n)
// TODO(!!!): For some reason Shamir's trick isn't working with
// signed message verification!? Probably an implementation
// error!
//var point = implShamirsTrick(G, u1, Q, u2)
var point = G.multiply(u1).add(Q.multiply(u2))
var point = G.multiplyTwo(u1, Q, u2)
var v = point.getX().toBigInteger().mod(n)
return v.equals(r)
@ -276,11 +245,11 @@ var ecdsa = {
// 1.5 Compute e from M
var e = BigInteger.fromBuffer(hash)
var eNeg = BigInteger.ZERO.subtract(e).mod(n)
var eNeg = e.negate().mod(n)
// 1.6 Compute Q = r^-1 (sR - eG)
var rInv = r.modInverse(n)
var Q = implShamirsTrick(R, s, G, eNeg).multiply(rInv)
var Q = R.multiplyTwo(s, G, eNeg).multiply(rInv)
Q.validate()
if (!ecdsa.verifyRaw(e, r, s, Q)) {