The Ethereum Metropolis Testnet implements the zksnark technology, which makes it possible to verify zero-knowledge-proof transactions within the ethereum network.
Here is the first zkSnark transaction:
https://ropsten.etherscan.io/tx/0x15e7f5ad316807ba16fe669a07137a5148973235738ac424d5b70f89ae7625e3#eventlog
Here is the code: zkSNARKs test code in solidity https://gist.github.com/chriseth/f9be9d9391efc5beb9704255a8e2989d
This is one of the exciting parts about the upcoming ethereum hardfork !
