The whole thing, drawn out
No maths on this page — just pictures. By the end you will know exactly what VeriPatra does when you hand it a file, and what each answer means.
The journey of one signed PDF
Five moments, from the signer's desk to your screen.
Someone writes an offer letter, an order or a certificate.
A fixed recipe turns the whole file into one long number.
The signer’s private key — on a token, card or secure chip — encrypts that number.
By WhatsApp, email or a printout with a QR code on it.
Squeeze again, unlock the stored number, compare. Match or no match.
The private key never leaves the signer, and the file never needs to be secret. That is the whole trick: anybody can check the signature, but only one person could have made it.
Who says the signer is who they claim?
A key proves someone signed. A certificate proves who. In India that chain ends at the Controller of Certifying Authorities.
The Government of India's root. VeriPatra ships its official trust roots.
Licensed by the CCA to issue certificates, and answerable to it.
Holds the private key. Their certificate names them and is signed by the CA above.
If the chain does not reach a recognised authority, the document is not automatically fake. It means nobody official is vouching for the signer — so VeriPatra returns amber, not red. Telling those two apart is the whole job.
What "changed after signing" looks like
You cannot see it with your eyes. The maths can see it instantly.
One line moved. Both numbers are the same length, and neither tells you what changed — only that something did. VeriPatra's "What changed?" analysis then narrows it down for you.
The four bands the engine can return
Each one has its own icon shape as well as its own colour, so the answer survives a low-resolution screenshot, a black-and-white printout, and red-green colour blindness. The plain-language screen folds these four into three verdicts — and keeps "could not check" separate from all of them, because a missed check is not a failed one.
Valid signature, recognised authority, nothing changed.
You can rely on this being the file that was signed.
The signature is real, but something is missing or unrecognised.
Verified with caveats — read the report before you act.
The file changed after signing, or the signature will not validate.
Treat this as untrustworthy until proven otherwise.
There is no digital signature in this PDF at all.
Not a failure — just nothing to check. Ask for a signed copy.