From 4411262c1ede7aead83a50ad3e1e5fc278306412 Mon Sep 17 00:00:00 2001
From: Chris Duncan <chris@zoso.dev>
Date: Wed, 6 Aug 2025 11:52:35 -0700
Subject: [PATCH] Eliminate redundant DataViews from BIP-44 ckd.

---
 src/lib/bip44-ckd.ts | 39 +++++++++++++++++++--------------------
 1 file changed, 19 insertions(+), 20 deletions(-)

diff --git a/src/lib/bip44-ckd.ts b/src/lib/bip44-ckd.ts
index 82bfdc3..a7c82ec 100644
--- a/src/lib/bip44-ckd.ts
+++ b/src/lib/bip44-ckd.ts
@@ -4,8 +4,8 @@
 import { BIP44_PURPOSE, HARDENED_OFFSET, SLIP10_ED25519 } from './constants'
 
 type ExtendedKey = {
-	privateKey: DataView<ArrayBuffer>
-	chainCode: DataView
+	privateKey: ArrayBuffer
+	chainCode: ArrayBuffer
 }
 
 export class Bip44Ckd {
@@ -30,35 +30,35 @@ export class Bip44Ckd {
 		const purposeKey = await this.CKDpriv(masterKey, BIP44_PURPOSE + HARDENED_OFFSET)
 		const coinKey = await this.CKDpriv(purposeKey, coin + HARDENED_OFFSET)
 		const accountKey = await this.CKDpriv(coinKey, account + HARDENED_OFFSET)
-		if (chain == null) return accountKey.privateKey.buffer
+		if (chain == null) return accountKey.privateKey
 		const chainKey = await this.CKDpriv(accountKey, chain)
-		if (address == null) return chainKey.privateKey.buffer
+		if (address == null) return chainKey.privateKey
 		const addressKey = await this.CKDpriv(chainKey, address)
-		return addressKey.privateKey.buffer
+		return addressKey.privateKey
 	}
 
 	static async slip10 (curve: string, S: ArrayBuffer): Promise<ExtendedKey> {
-		const key = new TextEncoder().encode(curve)
+		const key = new Uint8Array(new TextEncoder().encode(curve))
 		const data = new Uint8Array(S)
 		const I = await this.hmac(key, data)
-		const IL = new DataView(I.buffer.slice(0, I.length / 2))
-		const IR = new DataView(I.buffer.slice(I.length / 2))
+		const IL = I.buffer.slice(0, I.length / 2)
+		const IR = I.buffer.slice(I.length / 2)
 		return ({ privateKey: IL, chainCode: IR })
 	}
 
 	static async CKDpriv ({ privateKey, chainCode }: ExtendedKey, index: number): Promise<ExtendedKey> {
-		const key = new Uint8Array(chainCode.buffer)
+		const key = new Uint8Array(chainCode)
 		const data = new Uint8Array(37)
 		data.set([0])
 		data.set(this.ser256(privateKey), 1)
 		data.set(this.ser32(index), 33)
 		const I = await this.hmac(key, data)
-		const IL = new DataView(I.buffer.slice(0, I.length / 2))
-		const IR = new DataView(I.buffer.slice(I.length / 2))
+		const IL = I.buffer.slice(0, I.length / 2)
+		const IR = I.buffer.slice(I.length / 2)
 		return ({ privateKey: IL, chainCode: IR })
 	}
 
-	static ser32 (integer: number): Uint8Array {
+	static ser32 (integer: number): Uint8Array<ArrayBuffer> {
 		if (typeof integer !== 'number') {
 			throw new TypeError(`Expected a number, received ${typeof integer}`)
 		}
@@ -70,20 +70,19 @@ export class Bip44Ckd {
 		return new Uint8Array(view.buffer)
 	}
 
-	static ser256 (integer: DataView): Uint8Array {
-		if (!(integer instanceof DataView)) {
-			throw new TypeError(`Expected DataView, received ${typeof integer}`)
+	static ser256 (integer: ArrayBuffer): Uint8Array<ArrayBuffer> {
+		if (!(integer instanceof ArrayBuffer)) {
+			throw new TypeError(`Expected ArrayBuffer, received ${typeof integer}`)
 		}
 		if (integer.byteLength > 32) {
 			throw new RangeError(`Expected 32-byte integer, received ${integer.byteLength}-byte value: ${integer}`)
 		}
-		return new Uint8Array(integer.buffer)
+		return new Uint8Array(integer)
 	}
 
-	static async hmac (key: Uint8Array, data: Uint8Array): Promise<Uint8Array<ArrayBuffer>> {
-		const { subtle } = crypto
-		const pk = await subtle.importKey('raw', key, { name: 'HMAC', hash: 'SHA-512' }, false, ['sign'])
-		const signature = await subtle.sign('HMAC', pk, data)
+	static async hmac (key: Uint8Array<ArrayBuffer>, data: Uint8Array<ArrayBuffer>): Promise<Uint8Array<ArrayBuffer>> {
+		const pk = await crypto.subtle.importKey('raw', key, { name: 'HMAC', hash: 'SHA-512' }, false, ['sign'])
+		const signature = await crypto.subtle.sign('HMAC', pk, data)
 		return new Uint8Array(signature)
 	}
 }
-- 
2.47.3