HOTP IETF Draft David M’Raihi IETF Meeting - March 10, 2005

March 10, nd IETF Meeting2 Agenda OTP and Open Standards HOTP Algorithm Next Step and Conclusion

March 10, nd IETF Meeting3 Static Vs. One-Time Passwords Static Passwords are inadequate –Identity theft and phishing are real threats –Spyware, key loggers are common One Time Passwords: –Easy for users to understand & use anywhere –Moving target (more difficult to steal) Two-factor authentication –What you know (your PIN, password, etc.) –What you have (a token that generates OTP)

March 10, nd IETF Meeting4 Need for open standard for OTP Several algorithms exist but all private –Proprietary tokens are expensive –Standardization drives down costs for end users –Open standards foster innovation (e.g HTTP, TCP/IP) No easy way for people to –Analyze security, integration and deployment cost –Get a free, easily available description –Get a reference implementation

March 10, nd IETF Meeting5 OTP Algorithm: Requirements Usability –Easy to look up OTP value and enter in the application –User-friendly mechanisms to resynchronize the moving factor Security (algorithm and protocol) Implementation flexibility (SIM, tokens, software, etc.) Economical to implement in hardware

March 10, nd IETF Meeting6 HOTP Algorithm Based on known primitives –HMAC: RFC 2104 –SHA-1: FIPS 180-1, RFC 3174 Open Standards –All basic blocks are public, free to use –HOTP is also public anybody can implement it at no cost a reference implementation in Java is in the draft a detailed security analysis is also available

March 10, nd IETF Meeting7 HOTP Algorithm: Description HOTP (Counter, Key) = Truncate(HMAC-SHA-1 (Counter, Key)) The Key is a shared secret between the prover (HOTP token) and the verifier (HOTP validation server) The Counter is a moving factor that needs to be synchronized between the prover and the verifier

March 10, nd IETF Meeting8 SHA-1 Attacks: No impact HOTP is based on HMAC HMAC is not a hash function, it uses a hash function internally A MAC depends on a secret key The issues with MAC constructions is forgery, not collisions Best example: MD5 is broken, though no attack on HMAC-MD5

March 10, nd IETF Meeting9 HOTP algorithm in the real world Implemented in various flavors –Software Token to generate OTP values On PC, PDAs, any mobile device –Hardware Tokens OTP and hybrid tokens (with other functionalities) – SIM Cards GSM phones turn into tokens to generate OTPs

March 10, nd IETF Meeting10 Next Step and Conclusion HOTP as an RFC –Open Standard, Freely available –Reference implementations Today java, tomorrow C, javacard, etc. RFC status will drive adoption –Early adopters will innovate –Embedding algorithm in all devices –Improving security for internet users