IACR News item: 05 July 2015
Ahmed Kosba, Andrew Miller, Elaine Shi, Zikai Wen, Charalampos Papamanthou
ePrint Reporttocurrencies allow mutually distrustful parties to transact
safely with each other without trusting a third-party inter-
mediary. In the event of contractual breaches or aborts, the
decentralized blockchain ensures that other honest parties
obtain commesurate remuneration. Existing systems, how-
ever, lack transactional privacy. All transactions, including
flow of money between pseudonyms and amount trasacted,
are exposed in the clear on the blockchain.
We present Hawk, a decentralized smart contract system
that does not store financial transactions in the clear on
the blockchain, thus retaining transactional privacy from the
public\'s view. A Hawk programmer can write a private smart
contract in an intuitive manner without having to implement
cryptography, and our compiler automatically generates an
efficient cryptographic protocol where contractual parties in-
teract with the blockchain, using cryptographic primitives
such as succint zero-knowledge proofs.
To formally define and reason about the security of our
protocols, we are the first to formalize the blockchain model
of secure computation. The formal modeling is of indepen-
dent interest. We advocate the community to adopt such a
formal model when designing interesting applications atop
decentralized blockchains.
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