Adding encoders i decoders for signatures and points

src/index.ts

@@ -16,7 +16,7 @@ export type UnblindedSignature = { s: BigInteger, f: Point }
  * Imports a Point from hex string where X and Y coordinates were encoded as 32
  * & 32 bytes in LittleEndian.
  */
-export function importPointFromHex(pointHex: string) {
+export function pointFromHex(pointHex: string) {
     const xBuff = Buffer.from(pointHex.substr(0, 64), 'hex').reverse().toString('hex')
     const yBuff = Buffer.from(pointHex.substr(64), 'hex').reverse().toString('hex')
     const x = BigInteger.fromHex(xBuff)
@@ -25,20 +25,41 @@ export function importPointFromHex(pointHex: string) {
     return p
 }
 
+export function pointToHex(point: Point): string {
+    const buffX = point.affineX.toBuffer(32).reverse()
+    const buffY = point.affineY.toBuffer(32).reverse()
+
+    return buffX.toString("hex") + buffY.toString("hex")
+}
+
+export function signatureFromHex(hexSignature: string): UnblindedSignature {
+    if (!hexSignature || hexSignature.length != 192) throw new Error("Invalid hex signature (96 bytes expected)")
+
+    const s = BigInteger.fromBuffer(Buffer.from(hexSignature.substr(0, 64), "hex").reverse())
+    const f = pointFromHex(hexSignature.substr(64))
+    return { s, f }
+}
+
+export function signatureToHex(signature: UnblindedSignature): string {
+    if (!signature || !signature.f || !signature.s) throw new Error("The signature is empty")
+    const { f, s } = signature
+
+    // hex(swapEndiannes(s) ) + hex(f)
+    const flippedHexS = s.toBuffer(32).reverse().toString("hex")
+    return flippedHexS + pointToHex(f)
+}
+
+export function messageToBigNumber(message: string) {
+    const msg = Buffer.from(message, 'utf8')
+    return BigInteger.fromBuffer(msg)
+}
+
 export function newBigFromString(s: string) {
     let a = new BigInteger(null, null, null)
     a.fromString(s, null)
     return a
 }
 
-function random(bytes: number) {
-    let k: BigInteger
-    do {
-        k = BigInteger.fromByteArrayUnsigned(randomBytes(bytes)) as unknown as BigInteger
-    } while (k.toString() == '0' && k.gcd(n).toString() != '1')
-    return k
-}
-
 export function newKeyPair() {
     const sk = random(32)
     return { sk: sk, pk: G.multiply(sk) }
@@ -114,3 +135,13 @@ export function verify(m: BigInteger, s: UnblindedSignature, q: Point) {
     }
     return false
 }
+
+// HELPERS
+
+function random(bytes: number) {
+    let k: BigInteger
+    do {
+        k = BigInteger.fromByteArrayUnsigned(randomBytes(bytes)) as unknown as BigInteger
+    } while (k.toString() == '0' && k.gcd(n).toString() != '1')
+    return k
+}

test/index.test.ts

@@ -1,12 +1,11 @@
 import * as assert from 'assert'
 import * as BigInteger from 'bigi'
-import { Point } from 'ecurve'
 import { keccak256 } from '@ethersproject/keccak256'
 
-import { newBigFromString, ecparams, importPointFromHex, newKeyPair, newRequestParameters, blind, blindSign, unblind, verify } from '../src/index'
+import { pointFromHex, newKeyPair, newRequestParameters, blind, blindSign, unblind, verify, signatureFromHex, signatureToHex, messageToBigNumber, pointToHex } from '../src/index'
 
 describe('keccak256', function () {
-	it('keccak256', async () => {
+	it('should hash strings and big numbers', async () => {
 		const m = BigInteger.fromBuffer(Buffer.from('test', 'utf8'))
 		const mHex = m.toString(16)
 		const hHex = keccak256('0x' + mHex)
@@ -39,12 +38,36 @@ describe('test blind', function () {
 })
 
 describe('import point from hex', function () {
-	it('', async () => {
+	it('should import a point', async () => {
 		// pointHex and expected values was generated from
 		// go-blindsecp256k1 (Point.Bytes())
 		const pointHex = '73a68e845e626a2d7f683dd2ceb57956f755d623c0b729af30a72c7bf4dee7a6932d08955c98cf21edf35f5df218b56c41014db06f513cecc85dc3d8671f9521'
-		const p = importPointFromHex(pointHex)
+		const p = pointFromHex(pointHex)
 		assert.strictEqual('75493613315673782629634797792529672610524641864826422940379513836118869976691', p.x.toString())
 		assert.strictEqual('15189800969738851359449622716277258420468338317311652509571160848111971610003', p.y.toString())
+
+		assert.strictEqual(pointToHex(pointFromHex(pointHex)), pointHex)
+	})
+
+	it("should import a signature", () => {
+		const originalSignatureHex = "36cbb281c7d3f51fa6c027c39d1ec1115e72f4cf78beda1292ef16736894f327a77b4a7e7ba7b7daa54de6a111cb69b6a89bd8c15756a3d0bc620e77b134a9be2cf4d4758c2a5c59381f30bca694b585d9bbb192d349f7220b4e414503cd7eb6"
+		const { s, f } = signatureFromHex(originalSignatureHex)
+
+		assert.strictEqual(s.toString(10), "18070569205902663717816547129479407690196063715098828904678654635357913664310")
+		assert.strictEqual(f.affineX.toString(10), "86238402060026834577259540812071998074585426519937266202081591629132264536999")
+		assert.strictEqual(f.affineY.toString(10), "82544976118490904161760686015396902971720732626625394239692986344240783356972")
+
+		assert.strictEqual(signatureToHex(signatureFromHex(originalSignatureHex)), originalSignatureHex)
+	})
+
+	it("should import a signature with leading 0's on the big integers", () => {
+		const originalSignatureHex = "089a89f07bd41560454b1640fd30e51ee088d1be8355275a88e38a38f2e7a3000080fcc14af9c47c8066c6726e7d3cac9370494d5c67936b2978d6cecf5a4d00003ef00b060c47ba874c0764d662eff2d0e9daa8ba766f4aa6a2be8ec3d37500"
+		const { s, f } = signatureFromHex(originalSignatureHex)
+
+		assert.strictEqual(s.toString(10), "289596905226702587911033129111285060518391679824489553383063470810094737928")
+		assert.strictEqual(f.affineX.toString(10), "136673983650666514404918584888974483560635967304551499498329425981927620608")
+		assert.strictEqual(f.affineY.toString(10), "208182647280612121090241159906896377333338287898138605151276081386137599488")
+
+		assert.strictEqual(signatureToHex(signatureFromHex(originalSignatureHex)), originalSignatureHex)
 	})
 })