## Cryptology ePrint Archive: Report 2016/492

MiMC: Efficient Encryption and Cryptographic Hashing with Minimal Multiplicative Complexity

Martin Albrecht and Lorenzo Grassi and Christian Rechberger and Arnab Roy and Tyge Tiessen

Abstract: We explore cryptographic primitives with low multiplicative complexity. This is motivated by recent progress in practical applications of secure multi-party computation (MPC), fully homomorphic encryption (FHE), and zero-knowledge proofs (ZK) where primitives from symmetric cryptography are needed and where linear computations are, compared to non-linear operations, essentially free''. Starting with the cipher design strategy LowMC'' from Eurocrypt 2015, a number of bit-oriented proposals have been put forward, focusing on applications where the multiplicative depth of the circuit describing the cipher is the most important optimization goal.

Surprisingly, albeit many MPC/FHE/ZK-protocols natively support operations in \GF{p} for large $p$, very few primitives, even considering all of symmetric cryptography, natively work in such fields. To that end, our proposal for both block ciphers and cryptographic hash functions is to reconsider and simplify the round function of the Knudsen-Nyberg cipher from 1995. The mapping $F(x) := x^3$ is used as the main component there and is also the main component of our family of proposals called MiMC''. We study various attack vectors for this construction and give a new attack vector that outperforms others in relevant settings.

Due to its very low number of multiplications, the design lends itself well to a large class of new applications, especially when the depth does not matter but the total number of multiplications in the circuit dominates all aspects of the implementation. With a number of rounds which we deem secure based on our security analysis, we report on significant performance improvements in a representative use-case involving SNARKs.

Category / Keywords: distributed cryptography, cryptanalysis, block ciphers, hash functions, zero knowledge

Original Publication (with minor differences): IACR-ASIACRYPT-2016

Date: received 21 May 2016, last revised 5 Jan 2017

Contact author: christian rechberger at tugraz at

Available format(s): PDF | BibTeX Citation

Note: Added clarifications and Keccak benchmarks

Short URL: ia.cr/2016/492

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