| Paper ID | D6-S4-T1.1 |
| Paper Title |
The Discrepancy Attack on Polyshard-ed Blockchains |
| Authors |
Nastaran Abadi Khooshemehr, Mohammad Ali Maddah-Ali, Sharif University of Technology, Iran |
| Session |
D6-S4-T1: Blockchains |
| Chaired Session: |
Monday, 19 July, 23:00 - 23:20 |
| Engagement Session: |
Monday, 19 July, 23:20 - 23:40 |
| Abstract |
Sharding, i.e. splitting the miners or validators to form and run several subchains in parallel, is known as one of the main solutions to scalability problems of blockchains. The drawback is that as the number of miners expanding each subchain becomes small, it becomes vulnerable to security attacks. To solve this problem, a framework, named as \textit{Ployshard}, has been proposed in which each validator verifies a coded combination of the blocks introduced by different subchains, thus helping to protect the security of all subchains. In this paper, we introduce an attack on Ployshard, called \textit{the discrepancy} attack, which is the result of malicious nodes controlling a few subchains and dispersing different blocks to different nodes. We show that this attack undermines the security of Polyshard and is undetectable in its current setting.
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