One Time Password Authentication (otp)

Last Modifield: 2001-07-31

Concluded: 2002-10-29


Neil Haller <>
Ran Atkinson <>

Security Area Director(s):

Jeffrey Schiller <>
Steve Bellovin <>

Security Area Advisor:

Jeffrey Schiller <>

Mailing Lists:

General Discussion:
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Description of Working Group:

One form of attack on computing systems connected to the Internet is eavesdropping on network connections to obtain login id's and passwords of legitimate users [RFC 1704]. Bellcore's S/KEY(TM) one-time password system was designed to counter this type of attack, called a replay attack [RFC 1760]. Several one-time password implementations compatible with Bellcore's S/KEY (TM) system exist. These implementations are increasingly widely deployed in the Internet to protect against passive attacks.

The object of this working group is to write a standards track RFC for one-time password technology, using the technology in the Bellcore S/KEY system and related interoperable packages (e.g., logdaemon, NRL OPIE) as the basis for the group's effort. The standards-track RFC will enhance multi-vendor interoperability in one-time password authentication technologies and thereby help reduce security risks in the Internet.

General authentication servers are outside the scope of this working group. The ``S/Key-0'' system being considered for use in Kerberos is outside the scope of this working group.

The standards-track specification will describe how this one-time password technology can be used with at least the MD4, MD5, and SHA algorithms. The standard one-time password dictionary from RFC 1760 will be reused in order to maintain backwards compatibility with the various deployed systems, however, support for hexadecimal format passwords will also be mandatory to implement. The standard might specify passphrase quality checks for the secret passphrase. The standard will be specified so as to eliminate any possible conflict with the Bellcore trademark on the term ``S/Key.''

An Informational RFC might also be issued that describes conventions for the UNIX commands relating to one-time passwords, including command(s) to securely update a remote one-time password.

Goals and Milestones:

Done    Reach agreement on required and optional attributes.
Done    Produce Internet-Draft specifying the IETF one-time password authentication technology.
Done    Final review (Working Group Last Call) of the Internet-Draft.
Done    Submit One-Time Password document to IESG for consideration as a Proposed Standard.
Done    Submit Internet-Draft on optional extensions to OTP.
Done    Submit Internet-Draft on OTP optional Extensions to IESG for consideration of publication as an RFC.

No Current Internet-Drafts

Request For Comments:

A One-Time Password System (RFC 1938) (44844 bytes)
OTP Extended Responses (RFC 2243) (19730 bytes)
A One-Time Password System (RFC 2289) (56495 bytes)
The One-Time-Password SASL Mechanism (RFC 2444) (13408 bytes)