LAUSR

We investigate existing “password+hardware token”-based authentication schemes deployed in real-world applications and observe that they are vulnerable to critical threats. Specifically, a compromised manufacturer may issue a backdoored hardware token to a user and later recover the user’s secret, which is well known as backdoor attacks. Additionally, an authentication credential in these schemes consists of two parts: the one is derived from the password, the other one is derived from the hardware token. However, since the two parts are independent of each other, if an adversary can physically access the hardware token of a victim, he is able to break security of these schemes by performing dictionary-guessing attacks (DGA), which is called mislaying-then-DGA. In this paper, we design a non-interactively re-randomizable reverse firewall signature mechanism for securing hardware tokens, such that the user’s secret is well protected even if a backdoor is embedded. We also utilize a servers-aided password-based encryption mechanism to harden hardware tokens, so as to “seamlessly” integrate the two factors into one credential. Based on the above mechanisms, we develop a secure two-factor authentication scheme, dubbed ATTACH. We evaluate ATTACH in terms of security and efficiency to demonstrate it achieves a strong security guarantee with high efficiency.