From cbc35b58ce65e32eed6cb22496bd7673db0a760a Mon Sep 17 00:00:00 2001
From: Chris Duncan <chris@zoso.dev>
Date: Fri, 5 Dec 2025 06:49:03 -0800
Subject: [PATCH] Avoid string conversion when casting bigint to 32-byte
 buffer.

---
 src/lib/crypto/secp256k1.ts | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/lib/crypto/secp256k1.ts b/src/lib/crypto/secp256k1.ts
index 9857760..9c95e4d 100644
--- a/src/lib/crypto/secp256k1.ts
+++ b/src/lib/crypto/secp256k1.ts
@@ -310,11 +310,13 @@ export class Secp256k1 {
 
 	/** Number to 32b. Must be 0 <= num < 2²⁵⁶. validate, pad, to bytes. */
 	static bigintTo32Bytes (num: bigint): Bytes {
-		return this.hexToBytes(this
-			.bigintInRange(num, 0n, 2n ** 256n) // secp256k1 is weierstrass curve. Equation is x³ + ax + b.
-			.toString(16)
-			.padStart(this.L2, '0')
-		)
+		this.bigintInRange(num, 0n, 2n ** 256n) // secp256k1 is weierstrass curve. Equation is x³ + ax + b.
+		let len = this.L, bytes = new Uint8Array(len)
+		for (let i = len - 1; i >= 0; i--) {
+			bytes[i] = Number(num & 0xffn)
+			num >>= 8n
+		}
+		return bytes
 	}
 
 	/** Normalize private key to scalar (bigint). Verifies scalar is in range 1<s<N */
-- 
2.47.3