S/MIME

S/MIME, Secure Multipurpose Mail Extension
S/MIME is a secure standard from Deming Software and RSA Data Security to encrypt and/or authenticate MIME (Multipurpose Internet Mail Extensions) data. S/MIME defines a format for MIME data, the algorithms to be used for interoperability (RSA, RC2, SHA-1) and additional operational issues such as ANSI X.509 certificates and internet transport.