From 846802447090445e7eb3c1098cdb7120fb61833f Mon Sep 17 00:00:00 2001
From: Chris Duncan <chris@zoso.dev>
Date: Fri, 5 Dec 2025 14:07:51 -0800
Subject: [PATCH] Promote final point functions to static class members.

---
 src/lib/crypto/secp256k1.ts | 47 +++++++++++++++++++------------------
 1 file changed, 24 insertions(+), 23 deletions(-)

diff --git a/src/lib/crypto/secp256k1.ts b/src/lib/crypto/secp256k1.ts
index 8f72788..50c0068 100644
--- a/src/lib/crypto/secp256k1.ts
+++ b/src/lib/crypto/secp256k1.ts
@@ -15,8 +15,6 @@ type Point = {
 	X: bigint
 	Y: bigint
 	Z: bigint
-	toAffine: () => AffinePoint
-	toBytes: (isCompressed?: boolean) => Bytes
 }
 
 /** Alias to Uint8Array. */
@@ -208,6 +206,19 @@ export class Secp256k1 {
 		return this.Point(X3, Y3, Z3)
 	}
 
+	/** Convert point to 2d xy affine point. (X, Y, Z) ∋ (x=X/Z, y=Y/Z) */
+	static Affine (p: Point): AffinePoint {
+		const { X: x, Y: y, Z: z } = p
+		// fast-paths for ZERO point OR Z=1
+		if (this.Equals(p, this.I)) return { x: 0n, y: 0n }
+		if (z === 1n) return { x, y }
+		const iz = this.invert(z)
+		// (Z * Z^-1) must be 1, otherwise bad math
+		if (this.M(z * iz) !== 1n) this.err('inverse invalid')
+		// x = X*Z^-1; y = Y*Z^-1
+		return { x: this.M(x * iz), y: this.M(y * iz) }
+	}
+
 	/** Point doubling: P+P */
 	static Double (p: Point) {
 		return this.Add(p, p)
@@ -236,25 +247,6 @@ export class Secp256k1 {
 			X: this.bigintInRange(X, 0n, this.P),
 			Y: this.bigintInRange(Y, 1n, this.P), // Y can't be 0 in Projective
 			Z: this.bigintInRange(Z, 0n, this.P),
-			/** Convert point to 2d xy affine point. (X, Y, Z) ∋ (x=X/Z, y=Y/Z) */
-			toAffine (): AffinePoint {
-				const { X: x, Y: y, Z: z } = this
-				// fast-paths for ZERO point OR Z=1
-				if (secp256k1.Equals(this, secp256k1.I)) return { x: 0n, y: 0n }
-				if (z === 1n) return { x, y }
-				const iz = secp256k1.invert(z)
-				// (Z * Z^-1) must be 1, otherwise bad math
-				if (secp256k1.M(z * iz) !== 1n) secp256k1.err('inverse invalid')
-				// x = X*Z^-1; y = Y*Z^-1
-				return { x: secp256k1.M(x * iz), y: secp256k1.M(y * iz) }
-			},
-			/** Converts point to 33/65-byte Uint8Array. */
-			toBytes (isCompressed = true): Bytes {
-				const { x, y } = secp256k1.isValidPoint(this).toAffine()
-				const x32b = secp256k1.bigintTo32Bytes(x)
-				if (isCompressed) return secp256k1.concatBytes(secp256k1.getPrefix(y), x32b)
-				return secp256k1.concatBytes(Uint8Array.of(0x04), x32b, secp256k1.bigintTo32Bytes(y))
-			}
 		})
 	}
 
@@ -282,6 +274,14 @@ export class Secp256k1 {
 		return this.isValidPoint(p)
 	}
 
+	/** Converts point to 33/65-byte Uint8Array. */
+	static pointToBytes (p: Point, isCompressed = true): Bytes {
+		const { x, y } = this.Affine(this.isValidPoint(p))
+		const x32b = this.bigintTo32Bytes(x)
+		if (isCompressed) return this.concatBytes(this.getPrefix(y), x32b)
+		return this.concatBytes(Uint8Array.of(0x04), x32b, this.bigintTo32Bytes(y))
+	}
+
 	/** Generator / base point */
 	static G: Point = this.Point(this.Gx, this.Gy, 1n)
 	/** Identity / zero point */
@@ -310,7 +310,7 @@ export class Secp256k1 {
 	/** Checks if the point is valid and on-curve. */
 	static isValidPoint (p?: Point): Point {
 		if (p) {
-			const { x, y } = p.toAffine() // convert to 2d xy affine point.
+			const { x, y } = this.Affine(p) // convert to 2d xy affine point.
 			this.bigintInRange(x, 1n, this.P) // must be in range 1 <= x,y < P
 			this.bigintInRange(y, 1n, this.P)
 			// y² == x³ + ax + b, equation sides must be equal
@@ -327,7 +327,8 @@ export class Secp256k1 {
 
 	/** Creates 33/65-byte public key from 32-byte private key. */
 	static getPublicKey (sk: Bytes, isCompressed = true): Bytes {
-		return this.wNAF(this.secretKeyToScalar(sk)).p.toBytes(isCompressed)
+		const pk = this.pointToBytes(this.wNAF(this.secretKeyToScalar(sk)).p, isCompressed)
+		return this.isValidPublicKey(pk) ? pk : this.err('derived invalid public key from secret key')
 	}
 
 	static isValidPublicKey (pk: Bytes, isCompressed?: boolean): boolean {
-- 
2.47.3