When talking about .p7m files you often come across the term CAdES. But what exactly is it and why does it generate .p7m files? In this guide we explain the CAdES digital signature in a simple way.
What is CAdES
CAdES means *CAdES – CMS Advanced Electronic Signatures*: it is a European standard (eIDAS) for digital signature based on the PKCS#7 / CMS cryptographic format. A CAdES signature encloses the document in a signed envelope: the file you obtain has a .p7m extension.
Why CAdES produces .p7m files
With CAdES, any document — PDF, XML, Word, image — is "sealed" together with the signature in a single .p7m file. The signature guarantees:
- authenticity — who signed;
- integrity — that the file has not been modified;
- legal validity according to eIDAS.
CAdES vs PAdES: the difference
- CAdES → produces a .p7m file (the document is inside a signed envelope). This applies to any type of file.
- PAdES → sign inside the PDF itself: the file remains a normal .pdf that can be opened anywhere.
In Italy CAdES (.p7m) is widely used for invoices, deeds and PA communications; PAdES is convenient when you need a PDF that opens without tools.
How to open a CAdES signed file (.p7m)
With P7M Viewer:
1. Open the Open .p7m tool.
2. Upload the signed .p7m file to CAdES.
3. View or download the original document, and see who signed.
Frequently asked questions
Are CAdES and .p7m the same thing? In practice, yes: a CAdES signature produces a .p7m file.
Is CAdES legally valid? Yes, it is an eIDAS standard with full legal value.
How do I open a free CAdES? With P7M Viewer, free for a single file.
In summary
The CAdES signature is the standard that encloses a document in a signed .p7m envelope, guaranteeing authorship, integrity and legal value. To open it, all you need is P7M Viewer, in a few seconds and for free.
