Digital Signature Verification for .p7s, .sig and PDF Files

An online tool for verifying digital signatures: it opens .sig, .p7s and .p7m files, extracts the document from an attached signature and shows who signed it, when, and with which certificate. It checks RSA, RSA-PSS and ECDSA electronic signatures, Russian GOST R 34.10-2012 ones and signatures embedded in PDF files. The same page can also sign any file with your own key, producing a standard CMS signature.

How to verify a signature

Add the files

The signature (.sig, .p7s) and the document, together or one after the other. A signed PDF is a single file.

Who signed, when, and was it changed

Who signed, when, whether the document was changed and who issued the certificate — point by point.

Save what you need

The document from the signature, the signer’s certificate or a PDF verification report.

Open a .p7s, .sig or signed PDF and see who signed the document and when

Verification and signing run in your browser via WebCrypto

What the check shows

Who signedName, job title, organization, IDs in the certificate and the certificate authority
WhenSigning time, plus a trusted timestamp if there is one
Whether the document changedSHA or GOST R 34.11-2012 hash and the signature math
The document inside a .sigIf the document is inside the signature, you can open it and save it

RSA, ECDSA, GOST R 34.10-2012 and 2001, and signatures inside PDFs.

What the tool can do

RSA, ECDSA and GOST signatures

RSA, RSA-PSS and ECDSA, plus Russian GOST R 34.10-2012 and 2001 with all standard parameter sets: the signature math itself is checked, not just the text of the certificate.

The document inside a .p7m or .sig

When the signature is attached, the document is stored inside it — open it and save it with the right extension: .xml, .pdf, .docx.

Files pair up on their own

Drop the document and the signature together: they are paired by name, and by the document’s hash if the files were renamed.

Certificate details

Name, job title, organization, email, the IDs recorded in the certificate, the certificate authority and the validity period — on one card.

Signatures inside PDFs

See every signature in a PDF and whatever was added to the file after it; the signed version of the document can be downloaded separately.

Verification report

A PDF with every check and everything that was not checked — for correspondence, accounting and your records.

Common cases

Check a contract the other party sent with a detached .p7s or .sig signature and see who signed it.
Find out who signed a PDF from a government portal and whether anyone edited it afterwards.
Open a .p7m file and take out the document stored inside it.
Sign a file with your own key so the recipient can check who signed it and that it arrived unchanged.

How a signature is checked

A digital signature is, in essence, the document’s hash sealed with the signer’s private key. Verification recomputes the document’s hash with the same algorithm (SHA-2 for most signatures, GOST R 34.11-2012 “Streebog” for Russian ones) and compares it with the signed value: if even one byte differs, the document was changed. The signature itself is then checked with the public key from the certificate, and the dates show whether the certificate was valid at the moment of signing. A browser cannot establish certificate revocation or trust in the certificate authority, so the tool says so plainly; a legally binding validation of a qualified signature is the job of an officially recognized validation service (in the EU, a qualified validation service under eIDAS).

Frequently asked questions

How do I open a .p7s or .sig file?

A .p7s or .sig file is an electronic signature in CMS (PKCS#7) format; a .p7m is usually the same kind of signature with the document inside. Drop the file on this page: if the signature is attached, the document inside it can be opened and saved; if it is detached, add the document next to it and the check will show whether it was changed. There is no software to install.

Why is there no document inside my .p7s file?

That is how a detached signature works: it stores only the document’s hash and the certificate, while the document stays a separate file — usually under the same name without the signature extension, for example “Contract.pdf” and “Contract.pdf.p7s”. Add both files and they will be paired automatically, even if the names are different.

Can I verify a .p7s file on my phone without plugins?

Yes. The page works in the browser on Android and iPhone with no plugins or extra apps: RSA and ECDSA signatures are checked by the browser’s built-in WebCrypto, and GOST signatures by the page’s own code. Only the optional trusted timestamp, when you sign, goes through our server: the time server receives the signature’s hash.

Is this an official check of a qualified signature?

No. It checks that the document has not been changed, that the signature was made with the key in the certificate, and that the certificate was valid at the time of signing. Certificate revocation and trust in the certificate authority are not checked. For a legally binding validation of a qualified signature, use a qualified validation service in the EU, or the official service or certified software of the country whose authority issued the certificate.

What does “time stated by the signer” mean?

The signing time in the file is set by the signer’s computer, and its clock can be set to anything. If a trusted timestamp is attached to the signature, the time is confirmed by an independent server — this appears as a separate line in the check.

Will a tax office, court or public tender accept a signature made here?

Not where a qualified signature is required, and tax filings, public tenders and courts in many countries require one. A signature made with your own key is not qualified: in the EU the top level is a qualified electronic signature (QES) under eIDAS, and elsewhere it is a signature from an accredited or licensed certificate authority. A signature made here does prove that the file has not changed since signing, and it can be accepted when the parties agree to it.

How do I verify the signature in a PDF?

Add the PDF to the page, and the signatures inside it are found automatically. For each one you see the signer, the time and whether anything was added to the file after it; the signed version can be downloaded separately.

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Published 25 Jun 2026 Updated 26 Sep 2026 Author: The Supreme