Source : Free On-Line Dictionary of Computing

One-Time Password
     
         (OTP) A security system that requires a new
        password every time a user authenticates themselves.  OTP
        generates these passwords using either the {MD4} or {MD5}
        {hashing} {algorithms}.
     
        The equivalent term "S/Key" is a trademark of {Telcordia
        Technologies}, so the name OTP is used increasingly.
     
        See {RFC 1760} - "The S/KEY One-Time Password System" and {RFC
        1938} - "A One-Time Password System".
     
        {(http://www.cs.umd.edu/~harry/jotp/)}.
     
        (2000-01-31)