publications

2025

1. Reward-based Blockchain Infrastructure for 3D IC Supply Chain Provenance

   Sulyab Thottungal Valapu, Aritri Saha, Bhaskar Krishnamachari, and 2 more authors

   In 2025 IEEE International Symposium on Hardware Oriented Security and Trust (HOST), 2025

   To appear

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   In response to the growing demand for enhanced performance and power efficiency, the semiconductor industry has witnessed a paradigm shift toward heterogeneous integration, giving rise to 2.5D/3D chips. These chips incorporate diverse chiplets, manufactured globally and integrated into a single chip. Securing these complex 2.5D/3D integrated circuits (ICs) presents a formidable challenge due to inherent trust issues within the semiconductor supply chain. Chiplets produced in untrusted locations may be susceptible to tampering, introducing malicious circuits that could compromise sensitive information. This paper introduces an innovative approach that leverages blockchain technology to establish traceability for ICs and chiplets throughout the supply chain. Given that chiplet manufacturers are dispersed globally and may operate within different blockchain consortiums, ensuring the integrity of data within each blockchain ledger becomes imperative. To address this, we propose a novel dual-layer approach for establishing distributed trust across diverse blockchain ledgers. The lower layer comprises of a blockchain-based framework for IC supply chain provenance that enables transactions between blockchain instances run by different consortiums, making it possible to trace the complete provenance DAG of each IC. The upper layer implements a multi-chain reputation scheme that assigns reputation scores to entities while specifically accounting for high-risk transactions that cross blockchain trust zones. This approach enhances the credibility of the blockchain data, mitigating potential risks associated with the use of multiple consortiums and ensuring a robust foundation for securing 2.5D/3D ICs in the evolving landscape of heterogeneous integration.

   @inproceedings{thottungal_valapu_reward-based_2024,
     author = {Thottungal Valapu, Sulyab and Saha, Aritri and Krishnamachari, Bhaskar and Menon, Vivek and Guin, Ujjwal},
     title = {Reward-based {Blockchain} {Infrastructure} for {3D} {IC} {Supply} {Chain} {Provenance}},
     booktitle = {2025 IEEE International Symposium on Hardware Oriented Security and Trust (HOST)},
     year = {2025},
     note = {To appear}
   }

2023

1. DARSAN: A Decentralized Review System Suitable for NFT Marketplaces

   Sulyab Thottungal Valapu, Tamoghna Sarkar, Jared Coleman, and 5 more authors

   In Blockchain – ICBC 2023, 2023

   Abs DOI Bib HTML PDF

   We introduce DARSAN, a decentralized review system designed for Non-Fungible Token (NFT) marketplaces, to address the challenge of verifying the quality of highly resalable products with few verified buyers by incentivizing unbiased reviews. DARSAN works by iteratively selecting a group of reviewers (called “experts”) who are likely to both accurately predict the objective popularity and assess some subjective quality of the assets uniquely associated with NFTs. The system consists of a two-phased review process: a “pre-listing” phase where only experts can review the product, and a “pre-sale” phase where any reviewer on the system can review the product. Upon completion of the sale, DARSAN distributes incentives to the participants and selects the next generation of experts based on the performance of both experts and non-expert reviewers. We evaluate DARSAN through simulation and show that, once bootstrapped with an initial set of appropriately chosen experts, DARSAN favors honest reviewers and improves the quality of the expert pool over time without any external intervention even in the presence of potentially malicious participants.

   @inproceedings{thottungal_valapu_darsan_2023,
     author = {Thottungal Valapu, Sulyab and Sarkar, Tamoghna and Coleman, Jared and Avyukt, Anusha and Embrechts, Hugo and Torfs, Dimitri and Minelli, Michele and Krishnamachari, Bhaskar},
     editor = {Wang, Qin and Feng, Jun and Zhang, Liang-Jie},
     title = {DARSAN: A Decentralized Review System Suitable for NFT Marketplaces},
     booktitle = {Blockchain -- ICBC 2023},
     year = {2023},
     publisher = {Springer Nature Switzerland},
     address = {Cham},
     pages = {3--20},
     isbn = {978-3-031-44920-8},
     doi = {10.1007/978-3-031-44920-8_1},
     url = {https://doi.org/10.1007/978-3-031-44920-8_1},
   }

2022

1. A Survey of Probabilistic Micropayment Schemes

   Sulyab Thottungal Valapu, and Bhaskar Krishnamachari

   Mar 2022

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   Although the earliest electronic micropayment schemes date back to the mid-90s, recent years have witnessed a resurgence of research interest in the field due to the rising popularity of cryptocurrencies and the associated increase in transaction fees. Probabilistic micropayment schemes have shown particular theoretical promise due to their ability to aggregate payments beyond client-merchant pairs. In this paper, we review various probabilistic micropayment protocols proposed in both pre-cryptocurrency and post-cryptocurrency eras and provide an analysis of what the future of research in this field could look like.

   @techreport{thottungal_valapu_survey_2022,
     title = {A {Survey} of {Probabilistic} {Micropayment} {Schemes}},
     url = {https://blockchain.ieee.org/images/files/pdf/techbriefs-2022-q1/a-survey-of-probabilistic-micropayment-schemes.pdf},
     author = {Thottungal Valapu, Sulyab and Krishnamachari, Bhaskar},
     month = mar,
     year = {2022},
   }