How to open a .csig file
A .csig file is the CAdES signature Spain's AutoFirma writes. Drop it below to see the signed document and who signed it. Checked: that the document has not changed since signing and that the signature matches the certificate in the file. Not checked: the EU Trusted List and revocation. The file is not uploaded anywhere.
Nothing is uploaded. Only this page reads the file, in your browser. We count only that a file was opened (its format and the result), never its contents or name.
What a .csig file is
AutoFirma, the signing program of Spain's public administration, saves a CAdES signature with the .csig extension. Like a Polish .sig, it is a CMS structure (RFC 5652). An implicit signature carries the document inside it; an explicit one carries only the signature.
Explicit signatures
If the .csig holds only the signature, drop it together with the original document. The page finds the original by its digest, even under another name.
Other ways to open it
AutoFirma opens it once installed, and VALIDe, the Spanish government's validation service (https://valide.redsara.es), checks it after you upload the file. This page needs neither.