FlexiRand: Output Private (Distributed) VRFs and Application to Blockchains

Abstract

Web3 applications based on blockchains regularly need access to randomness that is unbiased, unpredictable, and publicly verifiable. For Web3 gaming applications, this becomes a crucial selling point to attract more users by providing credibility to the "random reward" distribution feature. A verifiable random function (VRF) protocol satisfies these requirements naturally, and there is a tremendous rise in the use of VRF services. As most blockchains cannot maintain the secret keys required for VRFs, Web3 applications interact with external VRF services via a smart contract where a VRF output is exchanged for a fee. While this smart contract-based plain-text exchange offers the much-needed public verifiability immediately, it severely limits the way the requester can employ the VRF service: the requests cannot be made in advance, and the output cannot be reused. This introduces significant latency and monetary overhead.