International Association for Cryptologic Research

International Association
for Cryptologic Research


KVaC: Key-Value Commitments for Blockchains and Beyond

Shashank Agrawal
Srinivasan Raghuraman
DOI: 10.1007/978-3-030-64840-4_28
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Presentation: Slides
Abstract: As blockchains grow in size, validating new transactions becomes more and more resource intensive. To deal with this, there is a need to discover compact encodings of the (effective) state of a blockchain --- an encoding that allows for efficient proofs of membership and updates. In the case of account-based cryptocurrencies, the state can be represented by a key-value map, where keys are the account addresses and values consist of account balance, nonce, etc. We propose a new commitment scheme for key-value maps whose size does not grow with the number of keys, yet proofs of membership are of constant-size. In fact, both the encoding and the proofs consist of just two and three group elements respectively (in groups of unknown order like class groups). Verifying and updating proofs involves just a few group exponentiations. Additive updates to key values enjoy the same level of efficiency too. Key-value commitments can be used to build dynamic accumulators and vector commitments, which find applications in group signatures, anonymous credentials, verifiable databases, interactive oracle proofs, etc. Using our new key-value commitment, we provide the most efficient constructions of (sub)vector commitments to date.
Video from ASIACRYPT 2020
  title={KVaC: Key-Value Commitments for Blockchains and Beyond},
  booktitle={Advances in Cryptology - ASIACRYPT 2020},
  author={Shashank Agrawal and Srinivasan Raghuraman},