A short survey of zk-Friendly Hash Functions

In this paper, we classify zk-friendly hash functions into three categories based on their inner structure. We explain the structures, name existing use cases, and analyze their performance. Blockchain technology itself and zero-knowledge proving systems used in blockchain applications rely heavily on hash functions. Consequently, there is a great need for arithmetization-oriented hash functions that will be optimal for in-circuit execution, i.e. be zk-friendly, and at the same time achieve the best possible native performance. This problem was addressed with the line of research that began developing in 2016 and has yielded numerous different hash functions since, most prominent ones being described in this paper.