Cryptology ePrint Archive: Report 2020/1161

KVaC: Key-Value Commitments for Blockchains and Beyond

Shashank Agrawal and Srinivasan Raghuraman

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.

Category / Keywords: cryptographic protocols / commitments, accumulators, blockchains, key-value, efficient, RSA

Original Publication (with minor differences): IACR-ASIACRYPT-2020

Date: received 23 Sep 2020, last revised 5 Oct 2020

Contact author: srini131293 at gmail com, shashank agraval@gmail com

Available format(s): PDF | BibTeX Citation

Note: Minor edits.

Version: 20201005:220335 (All versions of this report)

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