Add Point decode from hex

src/index.ts

@@ -1,7 +1,7 @@
 import { randomBytes } from 'crypto'
 import * as BigInteger from 'bigi'
 import { getCurveByName, Point } from 'ecurve'
-import { keccak256 } from "@ethersproject/keccak256"
+import { keccak256 } from '@ethersproject/keccak256'
 
 const ecparams = getCurveByName('secp256k1')
 const G = ecparams.G
@@ -12,6 +12,19 @@ export { ecparams }
 export type UserSecretData = { a: BigInteger, b: BigInteger, f: Point }
 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) {
+    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)
+    const y = BigInteger.fromHex(yBuff)
+    const p = Point.fromAffine(ecparams, x, y)
+    return p
+}
+
 export function newBigFromString(s: string) {
     let a = new BigInteger(null, null, null)
     a.fromString(s, null)
@@ -22,7 +35,7 @@ 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")
+    } while (k.toString() == '0' && k.gcd(n).toString() != '1')
     return k
 }
 

test/index.test.ts

@@ -1,13 +1,13 @@
 import * as assert from 'assert'
 import * as BigInteger from 'bigi'
-// import { Point } from 'ecurve'
-import { keccak256 } from "@ethersproject/keccak256"
+import { Point } from 'ecurve'
+import { keccak256 } from '@ethersproject/keccak256'
 
-import { newBigFromString, ecparams, newKeyPair, newRequestParameters, blind, blindSign, unblind, verify } from "../src/index"
+import { newBigFromString, ecparams, importPointFromHex, newKeyPair, newRequestParameters, blind, blindSign, unblind, verify } from '../src/index'
 
-describe("keccak256", function () {
-	it("keccak256", async () => {
-		const m = BigInteger.fromBuffer(Buffer.from("test", 'utf8'))
+describe('keccak256', function () {
+	it('keccak256', async () => {
+		const m = BigInteger.fromBuffer(Buffer.from('test', 'utf8'))
 		const mHex = m.toString(16)
 		const hHex = keccak256('0x' + mHex)
 		assert.strictEqual('0x9c22ff5f21f0b81b113e63f7db6da94fedef11b2119b4088b89664fb9a3cb658', hHex)
@@ -16,14 +16,14 @@ describe("keccak256", function () {
 	})
 })
 
-describe("test blind", function () {
-	it("should blind", async () => {
+describe('test blind', function () {
+	it('should blind', async () => {
 		const { sk, pk } = newKeyPair()
 
 		const { k, signerR } = newRequestParameters()
 
 		const msg = BigInteger.fromBuffer(
-			Buffer.from("test", 'utf8')
+			Buffer.from('test', 'utf8')
 		)
 		assert.strictEqual('1952805748', msg.toString())
 
@@ -37,3 +37,14 @@ describe("test blind", function () {
 		assert(verified)
 	})
 })
+
+describe('import point from hex', function () {
+	it('', async () => {
+		// pointHex and expected values was generated from
+		// go-blindsecp256k1 (Point.Bytes())
+		const pointHex = '73a68e845e626a2d7f683dd2ceb57956f755d623c0b729af30a72c7bf4dee7a6932d08955c98cf21edf35f5df218b56c41014db06f513cecc85dc3d8671f9521'
+		const p = importPointFromHex(pointHex)
+		assert.strictEqual('75493613315673782629634797792529672610524641864826422940379513836118869976691', p.x.toString())
+		assert.strictEqual('15189800969738851359449622716277258420468338317311652509571160848111971610003', p.y.toString())
+	})
+})