IC3: Advancing the science and applications of blockchains

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by Michael Mirkin, Yan Ji, Jonathan Pang, Ariah Klages-Mundt, Ittay Eyal, and Ari Juels on December 17, 2019
We have discovered a denial-of-service attack on Bitcoin-like blockchains that is much cheaper than previously described attacks. Such blockchains rely on incentives to provide security. We show how an attacker can disrupt those incentives to cause rational miners to stop mining.
by Itay Tsabary, Alexander Spiegelman, and Ittay Eyal on December 04, 2019
Proof-of-work (PoW) mechanisms secure about 80% of the $250B cryptocurrency market. PoW requires system participants to expend computational resources, and protects the system from attackers who cannot expend resources at an equivalent rate. These systems operate in the permissionless setting and compensate their users with cryptocurrency, having a monetary value. As cryptocurrency prices sore so do the invested resources, and Bitcoin expenditures alone are 0.24% of the global electricity consumption. Arguably, this is superfluous, and lowering the ecological footprint justifies settling for a lower attack threshold.
by Yujin Kwon, Jian Liu, Minjeong Kim, Dawn Song, and Yongdae Kim on September 30, 2019
Decentralization is an essential factor the should be inherently considered in the design of blockchain systems. Even though people design systems for good decentralization, in practice, we often observe that blockchain systems are highly centralized. Bitcoin and Ethereum, as representative examples, are already well known to be highly centralized in terms of network and mining. In fact, poor decentralization appears not only in PoW-based coins but also in coins adopting other mechanisms such as proof-of-stake (PoS) and delegated proof-of-stake (DPoS).
by Bryan Ford and Rainer Böhme on September 23, 2019
If you think you have designed a permissionless decentralized system that is cleverly secured based on rationality assumptions, you haven't. This blog post, based partly on ideas from Rainer Böhme's talk at the recent BDLT Summer School in Vienna, sketches an argument that rationality assumptions are self-defeating in open permissionless systems with weak identities.
by Fan Zhang, Steven Goldfeder, and Ari Juels on Tuesday September 03, 2019 at 02:00 PM
An oracle is a service that provides data to smart contracts or other systems. Oracles obtain their data from trusted websites. But even those that relay data correctly cannot safely access users' web-session data, because they can't enforce privacy. DECO is a privacy-preserving oracle protocol. Using cryptographic techniques, it lets users prove facts about their web (TLS) sessions to oracles while hiding privacy-sensitive data. DECO can make private and public web data accessible to a rich spectrum of applications, for blockchains and traditional (non-blockchain) systems.
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Featured Projects

HiveMind

HiveMind is a blockchain-based machine learning platform allowing participants to contribute data and train models in a fully decentralized way. It leverages federated learning to reduce overhead both in communication and computation. It combines a novel blockchain-based secure aggregation protocol with client-level differential privacy to prevent information leakage from the model parameters. For further details, please check out https://oblivm.com/hawk.

Keywords:
Decentralized
Computation
Machine Learning
Secure

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