Paper 2021/1535 Original: eprint.iacr.org/2021/1535 ↗

Light-OCB: Parallel Lightweight Authenticated Cipher with Full Security

Abstract

This paper proposes a lightweight authenticated encryption (AE) scheme, called Light-OCB, which can be viewed as a lighter variant of the CAESAR winner OCB as well as a faster variant of the high profi le NIST LWC competition submission LOCUS-AEAD. Light-OCB is structurally similar to LOCUS-AEAD and uses a nonce-based derived key that provides optimal security, and short-tweak tweakable blockcipher (tBC) for efficient domain separation. Light-OCB improves over LOCUS-AEAD by reducing the number of primitive calls, and thereby signi ficantly optimizing the throughput. To establish our claim, we provide FPGA hardware implementation details and benchmark for Light-OCB against LOCUS-AEAD and several other well-known AEs. The implementation results depict that, when instantiated with the tBC TweGIFT64, Light-OCB achieves an extremely low hardware footprint - consuming only around 1128 LUTs and 307 slices (signifi cantly lower than that for LOCUS-AEAD) while maintaining a throughput of 880 Mbps, which is almost twice as that of LOCUS-AEAD. To the best of our knowledge, this fi gure is signi ficantly better than all the known implementation results of other lightweight ciphers with parallel structures.