From: Chris Duncan <chris@zoso.dev>
Date: Wed, 30 Jul 2025 14:29:37 +0000 (-0700)
Subject: Refactor mnemonic validation to compare bitwise using bigints.
X-Git-Tag: v0.10.5~48^2~5
X-Git-Url: https://git.codecow.com/?a=commitdiff_plain;h=aa86d8dd095d890f2fd7e4612d32b85da6503bb9;p=libnemo.git

Refactor mnemonic validation to compare bitwise using bigints.
---

diff --git a/src/lib/bip39-mnemonic.ts b/src/lib/bip39-mnemonic.ts
index 47fe7cc..3d05afd 100644
--- a/src/lib/bip39-mnemonic.ts
+++ b/src/lib/bip39-mnemonic.ts
@@ -117,31 +117,38 @@ export class Bip39Mnemonic {
 			return false
 		}
 
-		const wordBits = words.map(word => {
+		let bits = 0n, bitLength = 0n
+		for (const word of words) {
 			const wordIndex = Bip39Words.indexOf(word)
 			if (wordIndex === -1) {
 				return false
 			}
-			return dec.toBin(wordIndex, 11)
-		}).join('')
-		const checksumLength = wordBits.length / 33
-		const entropyLength = wordBits.length - checksumLength
-		const entropyBits = wordBits.substring(0, entropyLength)
-		const checksumBits = wordBits.substring(entropyLength)
-
-		if (
-			entropyBits == null
-			|| entropyBits.length < 128
-			|| entropyBits.length > 256
-			|| entropyBits.length % 32 !== 0
+			bits = (bits << 11n) | BigInt(Bip39Words.indexOf(word))
+			bitLength += 11n
+		}
+		if (Number(bitLength) % 33 !== 0) {
+			return false
+		}
+
+		const checksumLength = bitLength / 33n
+		const entropyLength = Number(bitLength - checksumLength)
+		const entropyBits = bits >> checksumLength
+		const checksumBits = bits & ((1n << checksumLength) - 1n)
+
+		if (entropyBits == null
+			|| entropyBits < 0n
+			|| entropyBits > (1n << 256n) - 1n
+			|| entropyLength < 128
+			|| entropyLength > 256
+			|| entropyLength % 32 !== 0
 		) {
 			return false
 		}
 
-		const entropy = await Entropy.import(bin.toBytes(entropyBits))
+		const entropyHex = entropyBits.toString(16).padStart(entropyLength / 4, '0')
+		const entropy = await Entropy.import(entropyHex)
 		const expectedChecksum = await this.checksum(entropy.bytes)
-
-		if (Number(expectedChecksum) !== parseInt(checksumBits, 2)) {
+		if (expectedChecksum !== checksumBits) {
 			return false
 		}