This is a proof verifier following the zk-SNARK protocol of Parno et al. [PGHR13], for use with Zcash Sprout.
It is written in pure Rust and uses the bn pairing cryptography library, which uses the Barreto-Naehrig (BN) curve construction from [BCTV2015].
The proof verifier is written to closely resemble the verification procedure in figure 10 (page 25) of [BCTV2015].
Currently, its primary use is to independently verify the zero-knowledge proofs in the Zcash blockchain, which might be helpful if there turns out to be a bug in libsnark or in the way that the Zcash client uses libsnark.
All blocks in the Zcash main chain up to and including height 161007 (000000001ec1da40b9c5d8e7d26110bc8f239dfc0ca58685e92ee05903871a07) currently pass this verifier.
To reproduce, use the this rust-verifier branch of zcash, which should automatically download this Rust library and build as a dependency, and then make sure you start your node with -reindex to re-verify all zk-SNARK proofs. Warning: this will take a long time to complete for the whole chain.