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Replace unsigned signed_metadata with metadata + SHA-256 asset binding #39

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Replace unsigned signed_metadata with metadata + SHA-256 asset binding #39

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6d3858a
Initial plan
Copilot Mar 15, 2026
73bcbd3
Fix: Replace unsigned signed_metadata with metadata including SHA-256…
Copilot Mar 15, 2026
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10 changes: 2 additions & 8 deletions package-lock.json
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23 changes: 19 additions & 4 deletions src/services/UploadService.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -306,8 +306,8 @@ export class UploadService {
const filename = `screenshot_${Date.now()}.${asset.mimeType.split('/')[1]}`;
formData.append('asset_file', blob, filename);

const signedMetadata = this.createSignedMetadata(asset);
formData.append('signed_metadata', signedMetadata);
const metadata = await this.createMetadata(asset, blob);
formData.append('metadata', metadata);

if (asset.metadata?.headline) {
formData.append('headline', asset.metadata.headline);
Expand Down Expand Up @@ -444,10 +444,25 @@ export class UploadService {
}

/**
* Create signed metadata for upload
* Compute SHA-256 hash of a Blob using the Web Crypto API.
* Returns a lowercase hex-encoded digest string.
*/
private createSignedMetadata(asset: Asset): string {
private async computeSha256(blob: Blob): Promise<string> {
const arrayBuffer = await blob.arrayBuffer();
const hashBuffer = await crypto.subtle.digest('SHA-256', arrayBuffer);
const hashArray = Array.from(new Uint8Array(hashBuffer));
return hashArray.map(b => b.toString(16).padStart(2, '0')).join('');
}

/**
* Create metadata for upload, including a SHA-256 hash of the asset blob
* to cryptographically bind the image to its provenance metadata.
*/
private async createMetadata(asset: Asset, blob: Blob): Promise<string> {
const assetSha256 = await this.computeSha256(blob);

const metadata: any = {
asset_sha256: assetSha256,
spec_version: '2.0.0',
recorder: 'ProofSnap Browser Extension',
created_at: asset.createdAt,
Expand Down