From 1c6cd80b6414a0e1025720093111971343712acb Mon Sep 17 00:00:00 2001
From: Andras Schmelczer <andras@schmelczer.dev>
Date: Sat, 28 Mar 2026 12:07:44 +0000
Subject: [PATCH] Update hashing

---
 .../sync-client/src/sync-operations/syncer.ts     |  2 +-
 .../src/sync-operations/unrestricted-syncer.ts    |  6 +++---
 frontend/sync-client/src/utils/hash.ts            | 15 +++++----------
 3 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/frontend/sync-client/src/sync-operations/syncer.ts b/frontend/sync-client/src/sync-operations/syncer.ts
index eb5336f4..4cf92097 100644
--- a/frontend/sync-client/src/sync-operations/syncer.ts
+++ b/frontend/sync-client/src/sync-operations/syncer.ts
@@ -348,7 +348,7 @@ export class Syncer {
                     try {
                         const contentBytes =
                             await this.operations.read(relativePath); // this can throw FileNotFoundError
-                        return hash(contentBytes);
+                        return await hash(contentBytes);
                     } catch (e) {
                         if (
                             e instanceof Error &&
diff --git a/frontend/sync-client/src/sync-operations/unrestricted-syncer.ts b/frontend/sync-client/src/sync-operations/unrestricted-syncer.ts
index d32e983e..98a64f5d 100644
--- a/frontend/sync-client/src/sync-operations/unrestricted-syncer.ts
+++ b/frontend/sync-client/src/sync-operations/unrestricted-syncer.ts
@@ -101,7 +101,7 @@ export class UnrestrictedSyncer {
             const contentBytes = await this.operations.read(
                 document.relativePath
             ); // this can throw FileNotFoundError
-            const contentHash = hash(contentBytes);
+            const contentHash = await hash(contentBytes);
 
             let response: DocumentVersion | DocumentUpdateResponse | undefined =
                 undefined;
@@ -342,7 +342,7 @@ export class UnrestrictedSyncer {
                 {
                     documentId: remoteVersion.documentId,
                     parentVersionId: remoteVersion.vaultUpdateId,
-                    hash: hash(contentBytes),
+                    hash: await hash(contentBytes),
                     remoteRelativePath: remoteVersion.relativePath
                 },
                 this.database.createNewPendingDocument(
@@ -513,7 +513,7 @@ export class UnrestrictedSyncer {
 
         if (!("type" in response) || response.type === "MergingUpdate") {
             const responseBytes = base64ToBytes(response.contentBase64);
-            contentHash = hash(responseBytes);
+            contentHash = await hash(responseBytes);
 
             this.database.updateDocumentMetadata(
                 {
diff --git a/frontend/sync-client/src/utils/hash.ts b/frontend/sync-client/src/utils/hash.ts
index 906b6fad..814faefa 100644
--- a/frontend/sync-client/src/utils/hash.ts
+++ b/frontend/sync-client/src/utils/hash.ts
@@ -1,12 +1,7 @@
-// https://stackoverflow.com/questions/7616461/generate-a-hash-from-string-in-javascript
-export function hash(content: Uint8Array): string {
-    let result = 0;
-    // eslint-disable-next-line @typescript-eslint/prefer-for-of
-    for (let i = 0; i < content.length; i++) {
-        result = (result << 5) - result + content[i];
-        result |= 0; // Convert to 32bit integer
-    }
-    return Math.abs(result).toString(16).padStart(8, "0");
+export async function hash(content: Uint8Array): Promise<string> {
+    const digest = await crypto.subtle.digest("SHA-256", content);
+    const bytes = new Uint8Array(digest);
+    return Array.from(bytes, (b) => b.toString(16).padStart(2, "0")).join("");
 }
 
-export const EMPTY_HASH = hash(new Uint8Array(0));
+export const EMPTY_HASH = await hash(new Uint8Array(0));