S/MIME Vs RMS -Part II

Characteristic	S/MIME	RMS
Strong private key protection	Possible	Not possible
Private key storage	Disk (user profile), smart card	RM Account Certificate
usage rights (copy, print, forward)	No	Yes
Data rights can be configured to expire	No	Yes
Ease of use	Medium	Medium
Managerial efforts	High	Medium
Symmetric encryption algorithms	DES, 3DES, RC2 (Outlook)	DES, AES
Asymmetric encryption algorithms	RSA	RSA
PKI	Yes	No
Trust Relationship possible	Yes, through cross certification or sub-ordination	Trust relationships can be configured between RM Servers.
Compatibility	S/MIME, X.509 are cross-platform standards. S/MIME is implemented in most mail clients.	XrML is submitted as standard. IRM is only implemented in Outlook 2003; view-only functionality available in RMA. Additional clients can add IRM functionality through RM Client SDK.
Revocation checking	Done by the client (configurable), encrypted content is still accessible if cert not valid	Done by the server (when issuing EULs), encrypted content is not accessible once old licenses expire.
Expiration behavior	Expiration of the user's certificate does not affect decryption of encrypted files, but does prevent subsequent encryption of emails.	Expiration of user's RM account certificate will immediately prevent decryption of any existing or new RM-protected information.