Permutation-Based Lightweight Authenticated Cipher with Beyond Conventional Security

Abstract

Lightweight authenticated ciphers are specially designed as authenticated encryption (AE) schemes for resource-constrained devices. Permutation-based lightweight authenticated ciphers have gained more attention in recent years. However, almost all of permutation-based lightweight AE schemes only ensure conventional security, i.e., about $c/2$ -bit security, where $c$ is the capacity of the permutation. This may be vulnerable for an insufficiently large capacity. This paper focuses on the stronger security guarantee and the better efficiency optimization of permutation-based lightweight AE schemes. On the basis of APE series (APE, ${\text{APE}}^{RI}$ , ${\text{APE}}^{OW}$ , and ${\text{APE}}^{CA}$ ), we propose a new improved permutation-based lightweight online AE mode ${\text{APE}}^{+}$ which supports beyond conventional security and concurrent absorption. Then, we derive a simple security proof and prove that ${\text{APE}}^{+}$ enjoys at most about $\min \left\{r,c\right\}$ -bit security, where $r$ is the rate of the permutation. Finally, we discuss the properties of ${\text{APE}}^{+}$ on the hardware implementation.