@article{qiao_madathil_anyanwu_2022, title={Integrating Group Signatures in Complex Decentralized Marketplace Transactions for Improved Buyer Privacy}, DOI={10.1109/Blockchain55522.2022.00028}, abstractNote={Marketplace applications are a popular application category for blockchains because they allow the possibility for parties to transact without the need of a trusted middleman entity. Supply chain marketplaces involve buyers and sellers of goods and services that interact using complex transactional workflows rather than single, one-off transactions. Further, in some contexts, there is a need to maintain some degree of privacy about which parties are transacting and/or the nature of their transactions. Keeping such information private is often crucial for maintaining competitive advantage. However, traditional public key signature schemes do not provide strong enough privacy guarantees for such applications. On the other hand, signature schemes like Group Signatures offer more robust privacy guarantees but have not yet been adopted broadly in existing platforms. However, supporting privacy across multiple transactions in a workflow requires some extension to existing group signatures as opposed to just for a single transaction. In this paper, we present our effort on implementing some existing theoretical proposals for Group Signatures. We focus on application contexts in which it is sufficient to “hide” the originator of a transaction workflow i.e., the buyer (but is easily generalizable). Because, transaction workflows involve “multiple” related transactions which will be obfsucated by introducing privacy, we extend a group signature scheme with “linkability” of related transactions in a workflow under anonymity. We integrate our extended signature scheme into SmartChainDB - our extension of an open source blockchain platform, BigChainDB, that introduces several features for enabling complex marketplaces on blockchains.}, journal={2022 IEEE INTERNATIONAL CONFERENCE ON BLOCKCHAIN (BLOCKCHAIN 2022)}, author={Qiao, Sen and Madathil, Varun and Anyanwu, Kemafor}, year={2022}, pages={139–148} }
 @article{baldimtsi_madathil_scafuro_zhou_2020, title={Anonymous Lottery In The Proof-of-Stake Setting}, ISSN={["2374-8303"]}, DOI={10.1109/CSF49147.2020.00030}, abstractNote={When Proof-of-Stake (PoS) underlies a consensus protocol, parties who are eligible to participate in the protocol are selected via a public selection function that depends on the stake they own. Identity and stake of the selected parties must then be disclosed in order to allow verification of their eligibility, and this can raise privacy concerns. In this paper, we present a modular approach for addressing the identity leaks of selection functions, decoupling the problem of implementing an anonymous selection of the participants, from the problem of implementing others task, e.g. consensus. We present an ideal functionality for anonymous selection that can be more easily composed with other protocols. We then show an instantiation of our anonymous selection functionality based on the selection function of Algorand.}, journal={2020 IEEE 33RD COMPUTER SECURITY FOUNDATIONS SYMPOSIUM (CSF 2020)}, author={Baldimtsi, Foteini and Madathil, Varun and Scafuro, Alessandra and Zhou, Linfeng}, year={2020}, pages={318–333} }