## CryptoDB

### Paper: Forkcipher: A New Primitive for Authenticated Encryption of Very Short Messages

Authors: Elena Andreeva Virginie Lallemand Antoon Purnal Reza Reyhanitabar Arnab Roy Damian Vizár DOI: 10.1007/978-3-030-34621-8_6 Search ePrint Search Google Highly efficient encryption and authentication of short messages is an essential requirement for enabling security in constrained scenarios such as the CAN FD in automotive systems (max. message size 64 bytes), massive IoT, critical communication domains of 5G, and Narrowband IoT, to mention a few. In addition, one of the NIST lightweight cryptography project requirements is that AEAD schemes shall be “optimized to be efficient for short messages (e.g., as short as 8 bytes)”.In this work we introduce and formalize a novel primitive in symmetric cryptography called forkcipher. A forkcipher is a keyed primitive expanding a fixed-lenght input to a fixed-length output. We define its security as indistinguishability under a chosen ciphertext attack (for n-bit inputs to 2n-bit outputs). We give a generic construction validation via the new iterate-fork-iterate design paradigm.We then propose ${\mathsf {ForkSkinny}}$ as a concrete forkcipher instance with a public tweak and based on SKINNY: a tweakable lightweight cipher following the TWEAKEY framework. We conduct extensive cryptanalysis of ${\mathsf {ForkSkinny}}$ against classical and structure-specific attacks.We demonstrate the applicability of forkciphers by designing three new provably-secure nonce-based AEAD modes which offer performance and security tradeoffs and are optimized for efficiency of very short messages. Considering a reference block size of 16 bytes, and ignoring possible hardware optimizations, our new AEAD schemes beat the best SKINNY-based AEAD modes. More generally, we show forkciphers are suited for lightweight applications dealing with predominantly short messages, while at the same time allowing handling arbitrary messages sizes.Furthermore, our hardware implementation results show that when we exploit the inherent parallelism of ${\mathsf {ForkSkinny}}$ we achieve the best performance when directly compared with the most efficient mode instantiated with SKINNY.
##### BibTeX
@article{asiacrypt-2019-30037,
title={Forkcipher: A New Primitive for Authenticated Encryption of Very Short Messages},
booktitle={Advances in Cryptology – ASIACRYPT 2019},
series={Advances in Cryptology – ASIACRYPT 2019},
publisher={Springer},
volume={11922},
pages={153-182},
doi={10.1007/978-3-030-34621-8_6},
author={Elena Andreeva and Virginie Lallemand and Antoon Purnal and Reza Reyhanitabar and Arnab Roy and Damian Vizár},
year=2019
}