fix(point): handle point-at-infinity encoding per SEC1 (TOB-19)

Author: Stephen-Thomson

src/primitives/Point.ts

@@ -445,6 +445,10 @@ export default class Point extends BasePoint {
    * const encodedPointHex = aPoint.encode(true, 'hex');
    */
   encode (compact: boolean = true, enc?: 'hex'): number[] | string {
+    if (this.inf === true) {
+      if (enc === 'hex') return '00'
+      return [0x00]
+    }
     const len = this.curve.p.byteLength()
     const x = this.getX().toArray('be', len)
     let res: number[]

src/primitives/__tests/utils.test.ts

@@ -11,6 +11,7 @@ import {
   toBase58Check,
   verifyNotNull
 } from '../../primitives/utils'
+import Point from '../../primitives/Point'
 
 describe('utils', () => {
   it('should convert to array', () => {
@@ -359,3 +360,19 @@ describe('toUTF8 strict UTF-8 decoding (TOB-21)', () => {
 
 })
 
+describe('Point.encode infinity handling', () => {
+  it('encodes infinity as 00 (array)', () => {
+    const p = new Point(null, null)
+    expect(p.encode()).toEqual([0x00])
+  })
+
+  it('encodes infinity as 00 (hex)', () => {
+    const p = new Point(null, null)
+    expect(p.encode(true, 'hex')).toBe('00')
+  })
+
+  it('does not throw for infinity', () => {
+    const p = new Point(null, null)
+    expect(() => p.encode()).not.toThrow()
+  })
+})