Is there a decentralized zk-SNARK (zero-knowledge Succinct Non-Interactive ARgument of Knowledge)?
Here's Zcash's multi-party parameter calculation code, which...


  ... used a multi-party computation protocol with the property that the resulting parameters are secure unless all of the participants were dishonest or compromised during the ceremony.


By the way, you might find Bulletproofs more interesting which is newer and doesn't require a trusted setup.