International Association for Cryptologic Research

International Association
for Cryptologic Research


Farfalle: parallel permutation-based cryptography

Guido Bertoni , Security Pattern
Joan Daemen , STMicroelectronics; Radboud University
Seth Hoffert
Michaël Peeters , STMicroelectronics
Gilles Van Assche , STMicroelectronics
Ronny Van Keer , STMicroelectronics
DOI: 10.13154/tosc.v2017.i4.1-38
Search ePrint
Search Google
Abstract: In this paper, we introduce Farfalle, a new permutation-based construction for building a pseudorandom function (PRF). The PRF takes as input a key and a sequence of arbitrary-length data strings, and returns an arbitrary-length output. It has a compression layer and an expansion layer, each involving the parallel application of a permutation. The construction also makes use of LFSR-like rolling functions for generating input and output masks and for updating the inner state during expansion. On top of the inherent parallelism, Farfalle instances can be very efficient because the construction imposes less requirements on the underlying primitive than, e.g., the duplex construction or typical block cipher modes. Farfalle has an incremental property: compression of common prefixes of inputs can be factored out. Thanks to its input-output characteristics, Farfalle is really versatile. We specify simple modes on top of it for authentication, encryption and authenticated encryption, as well as a wide block cipher mode. As a showcase, we present Kravatte, a very efficient instance of Farfalle based on Keccak-p[1600, nr] permutations and formulate concrete security claims against classical and quantum adversaries. The permutations in the compression and expansion layers of Kravatte have only 6 rounds apiece and the rolling functions are lightweight. We provide a rationale for our choices and report on software performance.
  title={Farfalle: parallel permutation-based cryptography},
  journal={IACR Trans. Symmetric Cryptol.},
  publisher={Ruhr-Universit├Ąt Bochum},
  volume={2017, Issue 4},
  author={Guido Bertoni and Joan Daemen and Seth Hoffert and Michaël Peeters and Gilles Van Assche and Ronny Van Keer},