VRaaS: Verifiable Randomness as a Service on Blockchains

Jacob Gorman; Lucjan Hanzlik; Aniket Kate; Easwar Vivek Mangipudi; Pratyay Mukherjee; Pratik Sarkar; Sri AravindaKrishnan Thyagarajan

Paper 2024/957

VRaaS: Verifiable Randomness as a Service on Blockchains

Jacob Gorman, Supra Research

Lucjan Hanzlik, CISPA Helmholtz Center for Information Security

Aniket Kate, Supra Research, Purdue University West Lafayette

Easwar Vivek Mangipudi, Supra Research

Pratyay Mukherjee, Supra Research

Pratik Sarkar, Supra Research

Sri AravindaKrishnan Thyagarajan, University of Sydney

Abstract

Web3 applications, such as on-chain games, NFT minting, and leader elections necessitate access to unbiased, unpredictable, and publicly verifiable randomness. Despite its broad use cases and huge demand, there is a notable absence of comprehensive treatments of on-chain verifiable randomness services. To bridge this, we offer an extensive formal analysis of on-chain verifiable randomness services. We present the $first$ formalization of on-chain verifiable randomness in the blockchain setting by introducing the notion of Verifiable Randomness as a Service (VRaaS). We formally define VRaaS using an ideal functionality $\mathcal{F}_{\sf VRaaS}$ in the Universal Composability model. Our definition not only captures the core features of randomness services, such as unbiasability, unpredictability, and public verifiability, but also accounts for many other crucial nuances pertaining to different entities involved, such as smart contracts. Within our framework we study a generic design of Verifiable Random Function~(VRF)-based randomness service -- where the randomness requester provides an input on which the randomness is evaluated as VRF output. We show that it does satisfy our formal VRaaS definition. Furthermore, we show that the generic protocol captures many real-world randomness services like Chainlink VRF and Supra dVRF. We investigate whether our definition is minimalistic in terms of the desired security properties - towards that, we show that a couple of insecure constructions fall short of realizing our definition. Using our definition we also discover practical vulnerabilities in other designs such as Algorand beacon, Pyth VRF and Band VRF that offer on-chain verifiable randomness.

Note: Improved the author fields

Metadata

Available format(s): PDF
Category: Foundations
Publication info: Preprint.
Keywords: Randomness Service Blockchain Verifiable Random Function Smart Contract Universal Composability
Contact author(s): jacobgorman613 @ gmail com
hanzlik @ cispa de
aniket @ purdue edu
e mangipudi @ supraoracles com
pratyay85 @ gmail com
iampratiksarkar @ gmail com
t srikrishnan @ gmail com
History: 2024-06-18: revised; 2024-06-14: received; See all versions
Short URL: https://ia.cr/2024/957
License: CC BY

BibTeX

@misc{cryptoeprint:2024/957,
      author = {Jacob Gorman and Lucjan Hanzlik and Aniket Kate and Easwar Vivek Mangipudi and Pratyay Mukherjee and Pratik Sarkar and Sri AravindaKrishnan Thyagarajan},
      title = {{VRaaS}: Verifiable Randomness as a Service on Blockchains},
      howpublished = {Cryptology ePrint Archive, Paper 2024/957},
      year = {2024},
      note = {\url{https://eprint.iacr.org/2024/957}},
      url = {https://eprint.iacr.org/2024/957}
}