Since the last research update, IC3 researchers discovered a new method of bribing attacks on cryptocurrencies, proposed a Bitcoin payment protocol revision, pioneered a university DeFi course, and more!
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IC3 was proud to support the 2021 Cornell High School Programming Contest Warm Up and its goal to inclusively engage the next generation of programmers. The teams solved eight programming problems including one focused on blockchain. 
The authors present Mutual-Assured-Destruction Hashed Time-Locked Contract (MAD-HTLC), which utilizes miners as part of the design and prove its security and efficacy. If a user misbehaves, MAD-HTLC incentivizes the miners to confiscate all her funds. The authors also extend previous results regarding HTLC vulnerability to bribery attacks. 
Itay Tsabary (Technion, IC3), Matan Yechieli (Technion, IC3), Alex Manuskin (ZenGo-X), Ittay Eyal (Technion, IC3)

The authors introduce a distributed key generation (DKG) protocol with aggregatable and publicly-verifiable transcripts. It reduces the size of the final transcript and the time to verify it from O(n2) to O(n log n), where n denotes the number of parties and leverages gossip rather than all-to-all communication to reduce verification and communication complexity. They experimentally evaluate the DKG and show that the per party overheads scale linearly and are practical.
Kobi Gurkan (cLabs, Ethereum Foundation), Philipp Jovanovic (UCL), Mary Maller (Ethereum Foundation), Sarah Meiklejohn (UCL), Gilad Stern (Hebrew University), Alin Tomescu (VM Ware)
The authors give the first formal model of BIP70 and formalise the refund address security goals for the protocol. They confirm that the Payment Protocol is vulnerable to an attack violating the refund address authentication security goal and present a concrete protocol revision proposal.
Paolo Modestia Teesside University), Siamak F. Shahandashtib (University of York), Patrick McCorry (PISA Research), Feng Haod (University of Warwick)

The authors show that there is a statistically significant correlation between the profitability of mining and the total hash rate. They present a theoretical analysis showing that selfish mining under elastic hash supply leads either to the collapse of a chain or to a stable equilibrium depending on the attacker’s initial share.
Yoko Shibuya (NTT Research), Go Yamamoto (NTT Research), Fuhito Kojima (NTT Research), Elaine Shi (Cornell), Shin'ichiro Matsuo (Georgetown), Aron Laszka (University of Houston)

The authors summarize bribing attacks and similar techniques that leverage on programmatic execution and verification under the term algorithmic incentive manipulation (AIM) attacks. They present several research gaps and opportunities that warrant further investigation- particularly no- and near-fork attacks.
Aljosha Judmayer (SBA Research, Uni Wien), Nicholas Stifter (SBA Research, Uni Wien), Alexei Zamyatin (Imperial College London), Itay Tsabary (Technion, IC3), Ittay Eyal (Technion, IC3), Peter Gaži (IOHK), Sarah Meiklejohn (UCL), Edgar Weippl (Uni Wien)

The authors present a new method of bribing attacks on cryptocurrencies, Pay-To-Win (P2W), which is capable of facilitating double-spend collusion across different blockchains financed out-of-band. This technique can also be used to specifically incentivize transaction exclusion or (re)ordering. They use smart contracts to render the payment and receipt of bribes trustless. Their approach is approximately one order of magnitude cheaper than comparable bribing techniques.
Aljosha Judmayer (SBA Research, Uni Wien), Nicholas Stifter (SBA Research, Uni Wien), Alexei Zamyatin (Imperial College London), Itay Tsabary (Technion, IC3), Ittay Eyal (Technion, IC3), Peter Gaži (IOHK), Sarah Meiklejohn (UCL), Edgar Weippl (Uni Wien)

The authors develop a model of stable assets, including non-custodial stablecoins backed by cryptocurrencies. They derive fundamental results about dynamics and liquidity in stablecoin markets, demonstrate that these markets face deleveraging feedback effects that cause illiquidity during crises and exacerbate collateral drawdown, and suggest design improvements. They also introduce new attacks that exploit arbitrage-like opportunities around stablecoin liquidations.
Ariah Klages-Mundt and Andrea Minca (Both Cornell)

The authors propose a BFT SMR protocol that achieves optimal linear cost per decision under good networks and leaders, optimal quadratic cost per decision under bad networks, and remains always live.
Rati Gelashvili (Novi), Lefteris Kokoris-Kogias (Novi and IST Austria), Alexander Spiegelman (Novi), Zhuolun Xiang (UIUC)
Ari Juels (Cornell), Ittay Eyal (Technion), and Mahimna Kelkar (Cornell) published the Op-Ed “Miners, Front-Running-as-a-Service Is Theft” discussing issues raised by front-running-as-a-service (FaaS) as a response to miner/maximum extractable value (MEV). 
The Smart Contract Research Forum is an online forum for discussing the newest research around blockchains, smart contracts, and decentralized systems together with top industry teams. The Forum brings academic researchers, engineers, and industry leaders together to collaboratively define, design, and advance smart contract technology.
IC3 Faculty Member Dawn Song is co-instructing a course with Christine Parlour (both at Berkeley) on DeFi this semester. To our knowledge, it is the first university DeFi course. See the syllabus and slides at the PHDBA 297T.4 Decentralized Finance course website.
The authors of Bitcoin and Cryptocurrency Technologies minted the first NFT commemorating a textbook on opensea. There was an immediate counterfeit, which you can read about in Joseph Bonneu's tweet.
Please send any new research or presentations to to be included in the next research update.
Best wishes, 
Sarah Allen
IC3 Community Manager
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