From ed996117d8f03c7018285e7fab57b15b96937a2a Mon Sep 17 00:00:00 2001
From: Arseniy Klempner <arseniyk@status.im>
Date: Fri, 19 Dec 2025 12:22:41 -0800
Subject: [PATCH] fix: use viem for bytes32/bigint conversion

---
 packages/rln/src/proof.spec.ts  |  4 ++--
 packages/rln/src/utils/bytes.ts | 26 ++++----------------------
 packages/rln/src/utils/epoch.ts |  2 +-
 packages/rln/src/utils/hash.ts  |  2 +-
 packages/rln/src/zerokit.ts     |  8 ++++----
 5 files changed, 12 insertions(+), 30 deletions(-)

diff --git a/packages/rln/src/proof.spec.ts b/packages/rln/src/proof.spec.ts
index 6a1499db86..e032bb57b7 100644
--- a/packages/rln/src/proof.spec.ts
+++ b/packages/rln/src/proof.spec.ts
@@ -77,14 +77,14 @@ describe("RLN Proof Integration Tests", function () {
         BytesUtils.bytes32FromBigInt(element, "little")
       ),
       proofElementIndexes.map((index) =>
-        BytesUtils.writeUIntLE(new Uint8Array(1), index, 0, 1)
+        BytesUtils.writeUintLE(new Uint8Array(1), index, 0, 1)
       ),
       Number(rateLimit),
       0
     );
 
     const isValid = rlnInstance.zerokit.verifyRLNProof(
-      BytesUtils.writeUIntLE(new Uint8Array(8), testMessage.length, 0, 8),
+      BytesUtils.writeUintLE(new Uint8Array(8), testMessage.length, 0, 8),
       testMessage,
       proof,
       [BytesUtils.bytes32FromBigInt(merkleRoot, "little")]
diff --git a/packages/rln/src/utils/bytes.ts b/packages/rln/src/utils/bytes.ts
index 61d4528fae..fbf7fc47be 100644
--- a/packages/rln/src/utils/bytes.ts
+++ b/packages/rln/src/utils/bytes.ts
@@ -1,3 +1,4 @@
+import { bytesToBigInt, numberToBytes } from "viem";
 export class BytesUtils {
   /**
    * Concatenate Uint8Arrays
@@ -32,21 +33,13 @@ export class BytesUtils {
       return 0n;
     }
 
-    // Create a copy to avoid modifying the original array
     const workingBytes = new Uint8Array(bytes);
 
-    // Reverse bytes if input is little-endian to work with big-endian internally
     if (inputEndianness === "little") {
       workingBytes.reverse();
     }
 
-    // Convert to BigInt
-    let result = 0n;
-    for (let i = 0; i < workingBytes.length; i++) {
-      result = (result << 8n) | BigInt(workingBytes[i]);
-    }
-
-    return result;
+    return bytesToBigInt(workingBytes, { size: 32 });
   }
 
   /**
@@ -69,18 +62,7 @@ export class BytesUtils {
       );
     }
 
-    if (value === 0n) {
-      return new Uint8Array(32);
-    }
-
-    const result = new Uint8Array(32);
-    let workingValue = value;
-
-    // Extract bytes in big-endian order
-    for (let i = 31; i >= 0; i--) {
-      result[i] = Number(workingValue & 0xffn);
-      workingValue = workingValue >> 8n;
-    }
+    const result = numberToBytes(value, { size: 32 });
 
     // If we need little-endian output, reverse the array
     if (outputEndianness === "little") {
@@ -93,7 +75,7 @@ export class BytesUtils {
   /**
    * Writes an unsigned integer to a buffer in little-endian format
    */
-  public static writeUIntLE(
+  public static writeUintLE(
     buf: Uint8Array,
     value: number,
     offset: number,
diff --git a/packages/rln/src/utils/epoch.ts b/packages/rln/src/utils/epoch.ts
index bf89d40aa5..458ec46246 100644
--- a/packages/rln/src/utils/epoch.ts
+++ b/packages/rln/src/utils/epoch.ts
@@ -17,7 +17,7 @@ export function dateToEpoch(
 }
 
 export function epochIntToBytes(epoch: number): Uint8Array {
-  return BytesUtils.writeUIntLE(new Uint8Array(32), epoch, 0, 32);
+  return BytesUtils.writeUintLE(new Uint8Array(32), epoch, 0, 32);
 }
 
 export function epochBytesToInt(bytes: Uint8Array): number {
diff --git a/packages/rln/src/utils/hash.ts b/packages/rln/src/utils/hash.ts
index 43908ce45d..c7a39152a7 100644
--- a/packages/rln/src/utils/hash.ts
+++ b/packages/rln/src/utils/hash.ts
@@ -3,7 +3,7 @@ import { hash, poseidonHash as poseidon } from "@waku/zerokit-rln-wasm-utils";
 import { BytesUtils } from "./bytes.js";
 
 export function poseidonHash(...input: Array<Uint8Array>): Uint8Array {
-  const inputLen = BytesUtils.writeUIntLE(
+  const inputLen = BytesUtils.writeUintLE(
     new Uint8Array(8),
     input.length,
     0,
diff --git a/packages/rln/src/zerokit.ts b/packages/rln/src/zerokit.ts
index d39aebde85..ccf6fbda57 100644
--- a/packages/rln/src/zerokit.ts
+++ b/packages/rln/src/zerokit.ts
@@ -52,7 +52,7 @@ export class Zerokit {
       sha256(this.rlnIdentifier)
     );
     const pathElementsBytes = new Uint8Array(8 + pathElements.length * 32);
-    BytesUtils.writeUIntLE(pathElementsBytes, pathElements.length, 0, 8);
+    BytesUtils.writeUintLE(pathElementsBytes, pathElements.length, 0, 8);
     for (let i = 0; i < pathElements.length; i++) {
       // We assume that the path elements are already in little-endian format
       pathElementsBytes.set(pathElements[i], 8 + i * 32);
@@ -60,7 +60,7 @@ export class Zerokit {
     const identityPathIndexBytes = new Uint8Array(
       8 + identityPathIndex.length * 1
     );
-    BytesUtils.writeUIntLE(
+    BytesUtils.writeUintLE(
       identityPathIndexBytes,
       identityPathIndex.length,
       0,
@@ -73,8 +73,8 @@ export class Zerokit {
     const x = sha256(msg);
     return BytesUtils.concatenate(
       idSecretHash,
-      BytesUtils.writeUIntLE(new Uint8Array(32), rateLimit, 0, 32),
-      BytesUtils.writeUIntLE(new Uint8Array(32), messageId, 0, 32),
+      BytesUtils.writeUintLE(new Uint8Array(32), rateLimit, 0, 32),
+      BytesUtils.writeUintLE(new Uint8Array(32), messageId, 0, 32),
       pathElementsBytes,
       identityPathIndexBytes,
       x,