Source : Free On-Line Dictionary of Computing

Riordan's Internet Privacy Enhanced Mail
     
         (RIPEM) A (not yet complete, but useful)
        implementation of {Privacy Enhanced Mail} (PEM).  RIPEM allows
        your {electronic mail} to have the four security facilities
        provided by PEM: {disclosure protection} (optional),
        originator authenticity, message {integrity} measures and
        {non-repudiation} of origin (always).
     
        RIPEM was written primarily by Mark Riordan
        .  Most of the code is in the {public
        domain}, except for the {RSA} routines, which are a library
        called RSAREF licensed from {RSA Data Security, Inc}.
     
        The current (November 1993) version of RIPEM is 1.1a; the
        current version of the {Macintosh} {port} of RIPEM is 0.8b1.
     
        (1998-07-03)