You Reset I Attack! A Master Password Guessing Attack Against Honey Password Vaults

It is natural for Internet users to use a password vault to encrypt and manage numerous passwords with a master password. Using one to rule all that is handy but attackers can focus on breaking the vault by brute-force attacking the master password. The honey password vault is proposed to handle the above security concern. It traps the attacker by generating a plausible decoy vault when decrypting the password vault with a “guessing” master password, such that it is hard for the attacker to obtain the real vault. Following the seminal work (S&P’15), many schemes have been proposed to counter advanced attacks, e.g., the Kullback-Leibler divergence attack (CCS’16), encoding attack (USENIX Security’19), and intersection attack (USENIX Security’21). But we find that they barely capture the security after the master password is reset. Once the reset is completed, the attacker can identify the decoy vault by decrypting and comparing the old and new versions of a password vault. To prove this, we propose a new master password guessing attack (MPGA) to break all the existing honey password vault schemes. Experimental results show that MPGA can easily distinguish real and decoy vaults with 99.12%–100.00% accuracy. We further design a secure master-password-updatable honey password vault scheme, named SMART, to resist MPGA. SMART guarantees that the MPGA attacker decrypts out similar decoy vaults from the old and new versions of a password vault. We demonstrate that SMART restricts the attack performance of the MPGA to 49.88% (close to the ideal value 50.00%).