Differences and Commonalities Between S/MIME v3 and OpenPGP
S/MIME v3 and OpenPGP are both protocols for adding authentication and privacy to messages. However, they differ in many ways, and are not designed to be interoperable. Some cryptography algorithms are the same between the two protocols, but others differ. The following chart is a comparison of many relevant features of the two protocols, showing where they differ and where they are the same.| Mandatory features | S/MIME v3 | OpenPGP |
|---|---|---|
| Message format | Binary, based on CMS | Binary, based on previous PGP |
| Certificate format | Binary, based on X.509v3 | Binary, based on previous PGP |
| Symmetric encryption algorithm | TripleDES (DES EDE3 CBC) | TripleDES (DES EDE3 Eccentric CFB) |
| Signature algorithm | Diffie-Hellman (X9.42) with DSS or RSA | ElGamal with DSS |
| Hash algorithm | SHA-1 | SHA-1 |
| MIME encapsulation of signed data | Choice of multipart/signed or CMS format | multipart/signed with ASCII armor |
| MIME encapsulation of encrypted data | application/pkcs7-mime | multipart/encrypted |