Private Balance-Checking on Blockchain Accounts Using Private Integer Addition

Birenjith Sasidharan; Emanuele Viterbo

Paper 2022/950

Private Balance-Checking on Blockchain Accounts Using Private Integer Addition

Birenjith Sasidharan

, Government Engineering College Barton Hill

Emanuele Viterbo

, Monash University

Abstract

A transaction record in a sharded blockchain can be represented as a two-dimensional array of integers with row-index associated to an account, column-index to a shard and the entry to the transaction amount. In a blockchain-based cryptocurrency system with coded sharding, a transaction record of a given epoch of time is encoded using a block code considering the entries as finite-field symbols. Each column of the resultant coded array is then stored in a server. In the particular case of PolyShard scheme, the block code turns out to be a maximum-distance-separable code. In this paper, we propose a privacy-preserving multi-round protocol that allows a remote client to retrieve from a coded blockchain system the sum of transaction amounts belonging to two different epochs of time, but to the same account. At the core of the protocol lies an algorithm for a remote client to privately compute a non-linear function referred to as integer-addition of two finite-field symbols representing integer numbers, in the presence of curious-but-honest adversaries. Applying it to balance-checking in a cryptocurrency system, the protocol guarantees information-theoretic privacy on account number and shard number thereby ensuring perfect user anonymity, and also maintains confidentiality of half of the input bits on average. The protocol turns out to be a useful primitive for balance-checking in lightweight clients of a PolyShard-ed blockchain.

Note: This work is presented in 2022 IEEE International Symposium on Information Theory (ISIT) , Finland.

Metadata

Available format(s): PDF
Category: Cryptographic protocols
Publication info: Published elsewhere. 2022 IEEE International Symposium on Information Theory (ISIT), Finland
Keywords: blockchain pir balance checking privacy in blockchain
Contact author(s): birenjith @ gmail com
emanuele viterbo @ monash edu
History: 2022-07-23: approved; 2022-07-23: received; See all versions
Short URL: https://ia.cr/2022/950
License: CC BY

BibTeX

@misc{cryptoeprint:2022/950,
      author = {Birenjith Sasidharan and Emanuele Viterbo},
      title = {Private Balance-Checking on Blockchain Accounts Using Private Integer Addition},
      howpublished = {Cryptology {ePrint} Archive, Paper 2022/950},
      year = {2022},
      url = {https://eprint.iacr.org/2022/950}
}