From 6bb12ffb51a4c8516f623920c513651580bc2fca Mon Sep 17 00:00:00 2001
From: Chris Duncan <chris@codecow.com>
Date: Thu, 2 Jul 2026 23:58:59 -0700
Subject: [PATCH] Use bitwise ops instead of arithmetic where possible. Build
 mnemonic phrase string directly instead of using intermediate array.

---
 src/lib/crypto/bip39.ts | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/src/lib/crypto/bip39.ts b/src/lib/crypto/bip39.ts
index a00c755..37a5f26 100644
--- a/src/lib/crypto/bip39.ts
+++ b/src/lib/crypto/bip39.ts
@@ -17,7 +17,7 @@ export class Bip39 {
 	 * @returns {Promise<bigint>} First N/32 bits of the hash as a bigint
 	 */
 	static checksum (entropy: ArrayBuffer | Bytes): Promise<bigint> {
-		const checksumBitLength = (entropy.byteLength / 4) | 0
+		const checksumBitLength = entropy.byteLength >> 2
 		return crypto.subtle.digest('SHA-256', entropy)
 			.then(hash => {
 				const sha256sum = new Uint8Array(hash)[0]
@@ -46,25 +46,22 @@ export class Bip39 {
 		if (entropy.byteLength < 16 || entropy.byteLength > 32) {
 			throw new RangeError(`Entropy must be 16-32 bytes`)
 		}
-		if (entropy.byteLength % 4 !== 0) {
+		if (entropy.byteLength & 3) {
 			throw new RangeError(`Entropy must be a multiple of 4 bytes`)
 		}
 
-		const phraseLength = 0.75 * entropy.byteLength
+		const phraseLength = (entropy.byteLength >> 2) * 3
 		return this.checksum(entropy)
 			.then(checksum => {
-				const bigEntropy = bytes.toInt(entropy)
-
-				let concatenation: bigint = (bigEntropy << BigInt(entropy.byteLength) / 4n) | checksum
-				const words: string[] = []
+				let concatenation: bigint = (bytes.toInt(entropy) << BigInt(entropy.byteLength >> 2)) | checksum
+				let phrase = ''
 				for (let i = 0; i < phraseLength; i++) {
 					const wordBits = concatenation & 2047n
 					const wordIndex = Number(wordBits)
-					words.unshift(wordlist[wordIndex])
+					phrase = wordlist[wordIndex] + (i ? ' ' : '') + phrase
 					concatenation >>= 11n
 				}
-				const sentence = words.join(' ')
-				return this.fromPhrase(sentence)
+				return this.fromPhrase(phrase)
 			})
 	}
 
@@ -129,13 +126,13 @@ export class Bip39 {
 			|| entropyBits > (1n << 256n) - 1n
 			|| entropyLength < 128n
 			|| entropyLength > 256n
-			|| Number(entropyLength) % 32 !== 0
+			|| Number(entropyLength & 31n) !== 0
 		) {
 			return Promise.resolve(false)
 		}
-		const bytes = new Uint8Array(Number(entropyLength) / 8)
+		const bytes = new Uint8Array(Number(entropyLength >> 3n))
 		for (let i = 0; i < bytes.length; i++) {
-			const shift = entropyLength - (8n * BigInt(i + 1))
+			const shift = entropyLength - (BigInt(i + 1) << 3n)
 			const byte = (entropyBits >> shift) & 255n
 			bytes[i] = Number(byte)
 		}
-- 
2.52.0