Procedure
SHA-256 sealing, from document to verification link.
A description of the process executed when a file is uploaded, without going into cryptographic detail.
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Preparation
Formats other than PDF are converted in the browser. Word, PowerPoint, images and plain text are supported, subject to a limit of 50 MB per document.
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Sealing
A mark of approximately 6 mm at 15% opacity is applied to each page. No fonts or text blocks are embedded, so the layout remains intact.
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Fingerprint computation
The SHA-256 hash of the sealed document is calculated: 64 hexadecimal characters. Modifying a single byte produces an entirely different result.
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Registration
The fingerprint is recorded together with the file name, the date and a unique seal identifier. This is the only information transmitted.
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Verification
Any recipient may upload the document or open the public link. If the fingerprint matches the one on record, the file is identical to the one sealed.
Basis
A fingerprint that cannot be forged.
SHA-256 is a cryptographic hash function: it converts a file of any size into a fixed string of 64 characters. Three properties underpin the system.
- DeterminismThe same file always produces the same fingerprint, irrespective of the machine that computes it.
- SensitivityAltering a single bit produces an entirely different fingerprint, bearing no relation to the previous one.
- IrreversibilityThe fingerprint does not permit the source document to be reconstructed.
Publishing the fingerprint therefore does not compromise the content, and a matching fingerprint evidences that the file has not been modified.
From document to verification link, in seconds.
No installation or set-up. The recipient checks it from any browser.