RFC2289 - A One-Time Password System
- The current internet standard, as descended from the original S/Key specification.
- http://tools.ietf.org/html/rfc2289

IETF One Time Password Authentication Charter
- Current specifications for the official internet standard (a continuation of the BellCore S/Key standard). Composition and membership information included.
- http://www.ietf.org/html.charters/OLD/otp-charter.html

The S/KEY One-Time Password System
- Scholarly paper by Neil Haller on the original S/Key system. Links to many citations from the original paper.
- http://citeseer.ist.psu.edu/34338.html

otpCalc - An OTP and S/Key calculator for X
- otpCalc is an RFC2289 and RFC1760 compliant one time password calculator, written to use the GTK+ library for screen I/O.
- http://killa.net/infosec/otpCalc/

pilOTP
- OTP (S/Key) client for the Palm platform. Includes screen captures, and general information as well as software downloads.
- http://astro.uchicago.edu/home/web/valdes/pilot/pilOTP/

S/Key Introduction
- A technical description of the S/Key algorithm.
- http://www.surfnet.nl/innovatie/surf-ace/security/doc/skey.html

PyOTP
- A simple Python library, currently under development, to generate OTP (S/Key) responses. RFC-2289 compliant. Includes links to development and release information.
- http://pyotp.sourceforge.net/

DynaPass
- Provides primary or secondary authentication by regularly distributing passwords (or parts of passwords) through wireless phones. Time locked access.
- http://www.dynapass.com/

OTPC 9000
- An OTP (S/Key) calculator for Nokia 9000 cellular phones. Includes S/Key information and resources.
- http://www.basun.net/software/otpc/

PalmKey
- OTP (S/Key) calculator for palm pilots. Site includes information about both source and binary distributions.
- http://palmkey.sourceforge.net/

SkeyCalc
- OTP (S/Key) calculator for MacOS X, MacOS X Server and NEXTSTEP. RFC-2289 compliant. Site includes software downloads, documentation and an introduction to the technology.
- http://www.orange-carb.org/SkeyCalc/

JOTP Calculator
- A java applet OTP (S/Key) calculator. The applet downloads onto the client machine and calculates locally.
- http://www.cs.umd.edu/users/harry/jotp/

Clearview Systems
- Suppliers of Secure Computing SafeWord, a scheme based on hardware tokens. Includes rationale for single-use password systems, as well as other network security products.
- http://www.clearview.co.uk/

CRYPTOCard Network Security
- Password tokens delivered on key fobs, palm pilots, hardware or software. Security for dial in, access control, internet and web connections. Offers a strong two factor system. Management software. Includes rationale and business case for token-based acce
- http://www.cryptocard.com/