From 9c2fba56e0f68f976c1abe486f9fd3c6e93b437e Mon Sep 17 00:00:00 2001
From: polwex <polwex@sortug.com>
Date: Wed, 16 Jul 2025 11:59:08 +0700
Subject: 'm'

---
 lib/utils/bit.ts | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 lib/utils/bit.ts

(limited to 'lib/utils/bit.ts')

diff --git a/lib/utils/bit.ts b/lib/utils/bit.ts
new file mode 100644
index 0000000..bc1ed1a
--- /dev/null
+++ b/lib/utils/bit.ts
@@ -0,0 +1,35 @@
+import { sha256 } from "urbit-key-generation/src/utils";
+
+export function shas(buf: Buffer, salt: Buffer) {
+  return sha256(xor(salt, sha256(buf)));
+}
+
+export function xor(a: Buffer, b: Buffer) {
+  if (!Buffer.isBuffer(a) || !Buffer.isBuffer(b)) {
+    console.log("a", a);
+    console.log("b", b);
+    throw new Error("only xor buffers!");
+  }
+  const length = Math.max(a.byteLength, b.byteLength);
+  const result = new Uint8Array(length);
+  for (let i = 0; i < length; i++) {
+    result[i] = a[i] ^ b[i];
+  }
+  return result;
+}
+
+export function shaf(buf: Buffer, salt: Buffer) {
+  const result = shas(buf, salt);
+  const halfway = result.length / 2;
+  const front = result.slice(0, halfway);
+  const back = result.slice(halfway, result.length);
+  return xor(front, back);
+}
+
+export function hex2buf(hex: string) {
+  return Buffer.from(hex, "hex").reverse();
+}
+
+export function buf2hex(buf: Uint8Array) {
+  return Buffer.from(buf).reverse().toString("hex");
+}
-- 
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