CONTENT VERIFICATION
Seal Any File — Permanently
Your file never leaves your device. Only the cryptographic fingerprint is stored — permanently and tamper-proof.
Drop any file here to seal it
or click to browse · any file type · max 100 MB
HOW IT WORKS
How document sealing works
Select any file
Drag and drop or click to browse. Works with any file type: PDFs, images, code, ZIP archives, videos. Your file is never uploaded — it stays on your device.
Fingerprint in your browser
The Web Crypto API computes a SHA-256 hash entirely in your browser. This 64-character fingerprint is mathematically unique to your file's exact contents.
Sealed permanently
Only the fingerprint is sent to our server and recorded on Base blockchain via EAS. The timestamp and hash are permanently immutable and publicly verifiable.
Your file never uploads. Never.
The cryptographic fingerprint is computed entirely in your browser using the Web Crypto API. Attestum™ never sees, stores, or transmits your file. Only the 64-character fingerprint is sent to our server and sealed on the blockchain.
IDENTITY-BOUND SEALS
Prove you created it — not just that it exists
A standard seal proves a file existed at a specific moment. An identity-bound seal goes further: it permanently links your verified identity to the document. Anyone who checks the seal can see exactly who created it and when.
How it works
- 1
Sign in with your verified account
- 2
Drop your file to generate the seal
- 3
Your identity is permanently bound to the cryptographic proof
- 4
Anyone can verify both the file AND who sealed it
When to use identity-bound seals
Original creative work — prove authorship of designs, writing, code
Research data — bind your name to datasets and findings
Legal documents — prove who prepared or submitted a document
Business records — prove who authorized or created a report