Zerocoin

Zerocoin is a privacy protocol proposed in 2013 by Matthew D. Green and his graduate students Ian Miers and Christina Garman at Johns Hopkins University.

It extends the Bitcoin protocol to provide strong cryptographic anonymity by allowing coins to be 'minted' and 'redeemed' in a way that breaks the transaction history link, thus enabling anonymous transactions without trusted third parties.

The protocol uses cryptographic accumulators and zero-knowledge proofs to ensure unlinkability between coin minting and spending.

Zerocoin inspired the creation of cryptocurrencies like Zcoin (XZC) that implement this protocol natively.