One-Time Password

Synonyms

S/Key

(OTP) A security system that requires a new password every time a user authenticates themselves, thus protecting against an intruder replaying an intercepted password. OTP generates passwords using either the MD4 or MD5 hashing algorithms.

The equivalent term "S/Key", developed by Bellcore, 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".