Zerocash: Decentralized Anonymous Payments from Bitcoin

The cryptocurrency Zcash grew out of an MIT paper "Zerocash: Decentralized Anonymous Payments from Bitcoin," by Eli Ben-Sasson, Alessandro Chiesa, Christina Garman, Matthew Green, Ian Miers, Eran Tromer, and Madars Virza.

Zerocash is a protocol that provides a privacy-preserving version of Bitcoin (or a similar currency). Zerocash fixes an inherent weakness of Bitcoin: every user's payment history is recorded in public view on the block chain, and is thus readily available to anyone. While there are techniques to obfuscate this information, they are problematic and ineffective. Instead, in Zerocash, users may pay one another directly, via payment transactions that reveal neither the origin, destination, or amount of the payment. This is a marked improvement compared to Bitcoin (and similar decentralized digital currencies), where every payment's information is made public for the whole world to see.