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ecdsa: amend recoverPubKey SEC comments

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This commit is contained in:
Daniel Cousens 2014-06-14 11:47:22 +10:00
parent 4f8040f8d4
commit 402fa0d85d
1 changed files with 7 additions and 6 deletions
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13
src/ecdsa.js
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@ -210,10 +210,10 @@ function recoverPubKey(curve, e, signature, i) {
curve.P_OVER_FOUR = p.add(BigInteger.ONE).shiftRight(2)
}
// 1.1 Compute x
// 1.1 Let x = r + jn
var x = isSecondKey ? r.add(n) : r
// 1.3 Convert x to point
// 1.2, 1.3 Convert x to a point R using routine specified in Section 2.3.4
var alpha = x.pow(3).add(a.multiply(x)).add(b).mod(p)
var beta = alpha.modPow(curve.P_OVER_FOUR, p)
@ -221,16 +221,16 @@ function recoverPubKey(curve, e, signature, i) {
// 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
// 1.4 Check that nR is at infinity
var R = Point.fromAffine(curve, x, y)
var nR = R.multiply(n)
assert(curve.isInfinity(nR), 'nR is not a valid curve point')
// 1.5 Compute -e from e
// Compute -e from e
var eNeg = e.negate().mod(n)
// 1.6 Compute Q = r^-1 (sR - eG)
// Q = r^-1 (sR + -eG)
// 1.6.1 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)
@ -258,6 +258,7 @@ function calcPubKeyRecoveryParam(curve, e, signature, Q) {
for (var i = 0; i < 4; i++) {
var Qprime = recoverPubKey(curve, e, signature, i)
// 1.6.2 Verify Q
if (Qprime.equals(Q)) {
return i
}