Paper 2023/477 Original: eprint.iacr.org/2023/477 ↗

Separations between simulation-based and simulation-free formulations of security for public key encryption

Abstract

Simulation-based formulation of security enables us to naturally capture our intuition for security. However, since the simulation-based formulation is rather complicated, it is convenient to consider alternative simulation-free formulations which are easy to manipulate but can be employed to give the same security as the simulation-based one. So far the indistinguishability-based and comparison-based formulations have been introduced as such ones. Regarding the security for public key encryption, while these three formulations are shown equivalent in most settings, some relations among these formulations of non-malleability under the valid ciphertext condition, in which an adversary fails if it outputs an invalid ciphertext, remain open. This work aims to help to consider the appropriateness of the formulations of security by clarifying the above open relations among the formulations of non-malleable encryption.