A modified PBKDF2-based MAC scheme XKDF

PBKDF2 is a widely used password-based key derivation function as well as a message authentication code scheme. It is currently applied in Android backup file and Mac OS login security applications. In this paper, we propose a modified PBKDF2-based MAC scheme, denoted as XKDF. The proposed XKDF is provably secure for arbitrary-length message by the game-playing technique, which defined the upper-bound of adversary advantage. The practical safety of XKDF under the latest GPU-accelerated key recovery attack capability is also addressed.