# SoK of Used Cryptography in Blockchain

## TL;DR

This paper systematically reviews cryptographic concepts used in blockchain, highlighting current applications, potential future cryptographic solutions, and posing 21 open research challenges for cryptographers.

## Contribution

It provides the first comprehensive systematization of cryptographic concepts in blockchain, including unexploited techniques and future research directions.

## Key findings

- Cryptographic concepts currently used in blockchain are thoroughly cataloged.
- Potential cryptographic techniques not yet applied to blockchain are identified.
- 21 open research challenges are proposed for cryptographers.

## Abstract

The underlying fundaments of blockchain are cryptography and cryptographic concepts that provide reliable and secure decentralized solutions. Although many recent papers study the use-cases of blockchain in different industrial areas, such as finance, health care, legal relations, IoT, information security, and consensus building systems, only few studies scrutinize the cryptographic concepts used in blockchain. To the best of our knowledge, there is no Systematization of Knowledge (SoK) that gives a complete picture of the existing cryptographic concepts which have been deployed or have the potential to be deployed in blockchain. In this paper, we thoroughly review and systematize all cryptographic concepts which are already used in blockchain. Additionally, we give a list of cryptographic concepts which have not yet been applied but have big potentials to improve the current blockchain solutions. We also include possible instantiations of these cryptographic concepts in the blockchain domain. Last but not least, we explicitly postulate 21 challenging problems that cryptographers interested in blockchain can work on.