Blockchain-based criminal smart contract for symmetric key selling using ZK-SNARKs
G. Pavithra, Kunwar Singh · International Journal of Blockchains and Cryptocurrencies · 2023
Blockchain-based systems - Bitcoin, Ethereum, etc. - are very famous for various applications but, due to their properties like pseudo-anonymity, no central authority, they can pave way for criminal applications which are difficult to detect. We have proposed one such criminal application (which we call criminal smart contract) that can happen: on the blockchain, how a perpetrator can sell the symmetric key of a specific user to a contractor (who specifies his/her target user of interest) using ZK-SNARKs. We consider that the perpetrator has somehow already stolen/gotten to know the key of the user as specified by the contractor. Through this, we want to emphasise on the point that we have to devise methods to prevent the occurrence of various types of crimes in order to fully leverage the benefits of the blockchain. On this line, we have also provided few counter measures to avoid such cases of privacy and security issues.