Smart Contract-based Secure Verifiable Random Function using ChaCha20 Sequence in Blockchain

We provide a novel smart contract-based Verifiable Random Function (VRF) scheme that addresses the challenges associated with existing frameworks. Our suggested distributed VRF instantiation employs multi-party computation (MPC) within a blockchain network, ensuring collective randomness and security by preventing any singular participant from predicting the VRF's output. We endeavor to augment the stochastic nature of our VRF system by incorporating a cryptographically secure ChaCha20 sequence for the generation of pseudo-random sequences. We consider the forward security by adapting Identity-based Encryption (IBE) and show a cryptographic VRF construction, based on Elgamal Encryption and Discrete Logarithm Problem (DLP)-based cryptographic primitives with Decentralized Identifier (DID) for the MPC operations. The construction presents how to prove the correctness of the VRF's outputs with proofs, rendering it applicable for use cases necessitating random yet verifiable values. Moreover, we show the security analysis with formal proofs and entropy approximation for the randomness of the VRF output. Furthermore, employing the NIST SP800-22 randomness test suite for statistical randomness evaluation, our result shows an overall pass rate of 96.59% across a total of 176 tests encompassing 11 standard test cases. The average p -value is observed as 0.5728, indicative of relevant statistical randomness within the generated sequences. We also provide specific details on the implementation of our VRF scheme within a Solidity smart contract.