RU Sign
Verify a signed document
Drop a PDF signed with RU Sign: you will know if it is authentic and intact.
Upload a document signed with RU Sign. We recalculate its fingerprint and compare it with the one recorded at the time of signing. You will then know whether it is authentic and whether it has been modified since.
- Digital fingerprint (SHA-256). At signing, RU Sign computes a unique fingerprint from the exact bytes of the final PDF, then seals it.
- Recompute and compare. Here, we recompute the fingerprint of the file you upload and compare it with the one recorded at signing. If they are identical, the document is authentic and has not been modified.
- Server seal and timestamp. A seal (HMAC-SHA256) proves that it is indeed the RU Sign server that sealed the document, and an RFC 3161 timestamp certifies the signing date.
The fingerprint depends on every byte of the file. The smallest change, even invisible to the eye, produces a completely different fingerprint: the document is then no longer recognized as authentic. Here are common actions that alter the file without you realizing it:
- "Save as", "Print to PDF" or "Export as PDF" from a reader (Preview, Chrome, Edge, Acrobat...). Even if nothing changes on screen, the file is entirely rewritten with different bytes. Always use the original PDF downloaded from RU Sign, never a re-saved copy.
- Editing the text: adding, removing or replacing a single character - a period, a comma, an accent (é, à), or even a single space.
- Adding, deleting, reordering or rotating a page.
- Highlighting, annotating, adding a comment, filling a field or applying a stamp.
- "Optimizing", "compressing" or "reducing the size" of the PDF.
- Changing the file properties (title, author) or re-protecting it with a password.
- Taking a screenshot of the document and saving it again as a PDF: it is no longer the original file.
On the other hand: simply sending by email, forwarding or downloading does not modify the file. As long as these are the original bytes, verification remains valid. If in doubt, ask the sender for the original PDF again, or download it anew from your RU Sign dashboard.