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ecdsa: fixes edge case presented in #336

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This commit is contained in:
Daniel Cousens 2015-01-04 12:46:37 +11:00
parent 4c61380fa5
commit e9778ae358
3 changed files with 29 additions and 13 deletions
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2
package.json
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@ -52,7 +52,7 @@
"bs58check": "1.0.3",
"crypto-browserify": "^3.2.6",
"ecurve": "1.0.0",
"typeforce": "0.0.2"
"typeforce": "0.1.0"
},
"devDependencies": {
"async": "^0.9.0",

34
src/ecdsa.js
View file

@ -9,9 +9,10 @@ var ZERO = new Buffer([0])
var ONE = new Buffer([1])
// https://tools.ietf.org/html/rfc6979#section-3.2
function deterministicGenerateK(curve, hash, d) {
function deterministicGenerateK(curve, hash, d, checkSig) {
typeForce('Buffer', hash)
typeForce('BigInteger', d)
typeForce('Function', checkSig)
// sanity check
assert.equal(hash.length, 32, 'Hash must be 256 bit')
@ -55,8 +56,8 @@ function deterministicGenerateK(curve, hash, d) {
var T = BigInteger.fromBuffer(v)
// Step H3, repeat until T is within the interval [1, n - 1]
while ((T.signum() <= 0) || (T.compareTo(curve.n) >= 0)) {
// Step H3, repeat until T is within the interval [1, n - 1] and is suitable for ECDSA
while ((T.signum() <= 0) || (T.compareTo(curve.n) >= 0) || !checkSig(T)) {
k = crypto.createHmac('sha256', k)
.update(v)
.update(ZERO)
@ -64,6 +65,9 @@ function deterministicGenerateK(curve, hash, d) {
v = crypto.createHmac('sha256', k).update(v).digest()
// Step H1/H2a, again, ignored as tlen === qlen (256 bit)
// Step H2b again
v = crypto.createHmac('sha256', k).update(v).digest()
T = BigInteger.fromBuffer(v)
}
@ -71,18 +75,28 @@ function deterministicGenerateK(curve, hash, d) {
}
function sign(curve, hash, d) {
var k = deterministicGenerateK(curve, hash, d)
var r, s
var e = BigInteger.fromBuffer(hash)
var n = curve.n
var G = curve.G
var Q = G.multiply(k)
var e = BigInteger.fromBuffer(hash)
var r = Q.affineX.mod(n)
assert.notEqual(r.signum(), 0, 'Invalid R value')
deterministicGenerateK(curve, hash, d, function(k) {
var Q = G.multiply(k)
var s = k.modInverse(n).multiply(e.add(d.multiply(r))).mod(n)
assert.notEqual(s.signum(), 0, 'Invalid S value')
if (curve.isInfinity(Q))
return false
r = Q.affineX.mod(n)
if (r.signum() === 0)
return false
s = k.modInverse(n).multiply(e.add(d.multiply(r))).mod(n)
if (s.signum() === 0)
return false
return true
})
var N_OVER_TWO = n.shiftRight(1)

6
test/ecdsa.js
View file

@ -15,12 +15,14 @@ var fixtures = require('./fixtures/ecdsa.json')
describe('ecdsa', function() {
describe('deterministicGenerateK', function() {
function checkSig() { return true }
fixtures.valid.forEach(function(f) {
it('for \"' + f.message + '\"', function() {
var d = BigInteger.fromHex(f.d)
var h1 = crypto.sha256(f.message)
var k = ecdsa.deterministicGenerateK(curve, h1, d)
var k = ecdsa.deterministicGenerateK(curve, h1, d, checkSig)
assert.equal(k.toHex(), f.k)
})
})
@ -35,7 +37,7 @@ describe('ecdsa', function() {
var d = new BigInteger('1')
var h1 = new Buffer(32)
var k = ecdsa.deterministicGenerateK(curve, h1, d)
var k = ecdsa.deterministicGenerateK(curve, h1, d, checkSig)
assert.equal(k.toString(), '42')
}))