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

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:

• CryptMsgOpenToDecode
• CryptMsgUpdate
• CryptMsgClose
• CryptMsgGetParam
• CryptDecodeObject
• CryptFindOIDInfo

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

Related:

• PKCS #7 - Cryptographic Message Syntax Standard
• Outlook Express Does Not Use 3DES to Encrypt Mail When the Recipient's Capabilities Are Not Known
  
• OLEXP: Outlook Express Does Not Send 128 -Bit Encrypted E-mail Messages by Using Digital IDs
  
• Outlook Express RC2 40 --> 3DES patch
  
• Advanced Security Information
  

Michel I. Gallant
neutron@istar.ca