On Password Hashing and Password Hardening Schemes (G21b)
Passwords are the most cost effective and widely deployed means of human-computer authentication regardless of their vulnerability to dictionary attacks. Password hashing schemes (PHSs) compute password hashes, typically to be stored at authentication servers, with the aim to slow down the dictionary attacks on passwords by increasing the work factor (in terms of time and memory) needed to test each password candidate. Recent efforts by cryptographers during and after the password hashing competition resulted in new design strategies for PHSs. However, due to the advancements on dedicated hardware devices (e.g., GPUs, ASIC, FPGAs) in terms of number of computations per unit time, PHSs are not very effective when the passwords have low entropy. Another approach that is recently popularized is using password hardening schemes that distribute the authentication data between an authentication server and an external crypto-server (or a hardware security module) that can process a cryptographic operation using its secret key. In this talk, we provide an overview of current password hashing and password hardening schemes, and give insights on the standardization efforts of NIST.