Decryption Failure Is More Likely After Success

Abstract

The user of an imperfectly correct lattice-based public-key encryption scheme leaks information about their secret key with each decryption query that they answer—even if they answer all queries successfully. Through a refinement of the D’Anvers–Guo–Johansson–Nilsson–Vercauteren–Verbauwhede failure boosting attack, we show that an adversary can use this information to improve his odds of finding a decryption failure. We also propose a new definition of (Formula Presented)-correctness, and we re-assess the correctness of several submissions to NIST’s post-quantum standardization effort.