AuthAttr: Display Certificates and PKCS #7 Signed Message Authenticated Attributes

AuthAttr is a .NET assembly CryptoAPI console utility which lists certificates and the Authenticated Attributes information for a CMS/PKCS #7 signed message file. It also lists all certificates in PKCS #7 certificate store files. Both binary DER and base64 file formats are supported.

If the SMIMECapabilities attribute (1.2.840.113549.1.9.15) is found, the S/MIME Capabilities (typically encryption preferences) are decoded and listed. S/MIME capable email clients use the SMIMECapabilities attribute in received signed email messages to know the (ordered) encryption preferences of the sender.

Other Authenticated Attributes are not decoded in this utility, but can be easily handled the same way.

This utility uses P/Invoke to CryptoAPI functions:

C# Source
Sample output
SMIMECapabilities sent by various S/MIME email clients


Michel I. Gallant