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Uses low 's' values for signatures

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This commit is contained in:
GreenAddress.it 2014-04-17 06:05:41 +02:00
parent 3219e5e727
commit d7c2e4d5a5
2 changed files with 22 additions and 0 deletions
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5
src/ecdsa.js
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@ -69,6 +69,11 @@ var ecdsa = {
var s = k.modInverse(n).multiply(e.add(d.multiply(r))).mod(n)
if (s.compareTo(n.divide(BigInteger.valueOf(2))) > 0) {
// Make 's' value 'low', as per https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki#low-s-values-in-signatures
s = n.subtract(s);
}
return ecdsa.serializeSig(r, s)
},

17
test/eckey.js
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@ -1,4 +1,8 @@
var assert = require('assert')
var ecdsa = require('../src/ecdsa.js')
var sec = require('../src/jsbn/sec.js')
var BigInteger = require('../src/jsbn/jsbn.js')
var ecparams = sec("secp256k1")
var ECKey = require('../src/eckey.js').ECKey
var ECPubKey = require('../src/eckey.js').ECPubKey
var convert = require('../src/convert.js')
@ -148,6 +152,19 @@ describe('ECKey', function() {
assert(priv.verify(message, signature))
})
it('should sign with low S value', function() {
var priv = new ECKey(hpriv)
var signature = priv.sign(message)
var parsed = ecdsa.parseSig(signature)
// Check that the 's' value is 'low', to prevent possible transaction malleability as per
// https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki#low-s-values-in-signatures
assert(parsed.s.compareTo(ecparams.getN().divide(BigInteger.valueOf(2))) <= 0)
assert(priv.verify(message, signature))
})
it('should verify against the public key', function() {
var priv = new ECKey(hpriv)
var pub = new ECPubKey(hcpub, true)