Dasta – Alternative Linear Layer for Rasta

  • Phil Hebborn Ruhr University Bochum, Bochum, Germany
  • Gregor Leander Ruhr University Bochum, Bochum, Germany
Keywords: Symmetric encryption, FHE, multiplicative complexity, multiplicative depth, Rasta

Abstract

Progress in the areas of multi-party computation (MPC) and fully homomorphic encryption (FHE) caused the demand of new design strategies, that minimize the number of multiplications in symmetric primitives. Rasta is an approach for a family of stream ciphers with an exceptional low AND depth, which equals the number of ANDs per encrypted bit. This is achieved in particular by randomizing parts of the computation with the help of a PRNG, implying that the security arguments rely on the provided randomness and the encryption/ decryption is potentially slowed down by this generation.
In this paper we propose a variant of Rasta that achieves the same performance with respect to the AND depth and the number of ANDs per encrypted bit, but does not rely on a PRNG, i.e. is based on fixed linear layers.

Published
2020-09-28
How to Cite
Hebborn, P., & Leander, G. (2020). Dasta – Alternative Linear Layer for Rasta. IACR Transactions on Symmetric Cryptology, 2020(3), 46-86. https://doi.org/10.13154/tosc.v2020.i3.46-86
Section
Articles