Overview#Cryptographic Message Syntax or (CMS) is the IETF's standard for Cryptographically protected messages.
Cryptographic Message Syntax can be used to digitally sign, digest, authenticate or encrypt any form of digital data.
Cryptographic Message Syntax (as of 2009) is specified in RFC 5652 (but see also RFC 5911 for updated ASN.1 modules conforming to ASN.1 2002).
Cryptographic Message Syntax architecture is built around certificate-based Key management, such as the profile defined by the PKIX working group.
OpenSSL is open source software that can encrypt, decrypt, sign and verify, compress and uncompress CMS documents.