Tracking Issue: Validate Transactions

[yaahc]

Flesh out zebra-chain and dependencies as needed to be able to validate a single transaction. This is enough extensive work that feeds into our Sync and validate the chain milestone.

Remaining chunks of work in approximate priority order:

• implementing tree state management for Sapling (assuming checkpointing on Sapling activation)
  • nullifier set Nullifier Set #289
  • sapling note commitment (merkle) tree Implement Sapling note commitment tree #286 Implement Sprout Note Commitment Function #273
    • type out notes Type out Sprout and Sapling Notes #275
    • pull in merkle-tree hash functions and pedersen commitments Pedersen Hash (at least for use in the Sapling merkle tree) #334
• the remaining pieces of validation
  • Spend, Output, and JoinSplit proof statements
    • Depends on Groth16 validation service - Implement verifiers that accept Groth16 types #305, maybe Implement Groth16 batch verification optimizations #406, Asynchronous Groth16 verification #830
      • Which calls to bellman
  • SIGHASH?
• consensus rules stuff - https://github.com/ZcashFoundation/zebra/issues?q=is%3Aissue++label%3Aconsensus+
• script impl
  • wrap zcash's zcashconsensus library and re-export it as a rust crate - Wrap and re-export zcashconsensus as a rust crate #622
    • integrate zcashconsensus with zebra-consensus Make zebra-script wrap the C++ script implementation in zcashconsensus #708
      • publish the zcashconsensus crate so we don't have to use it as a git dependency
      • implement UTXO set tracking for inputs into verify_script
      • add prerequisite consensus parameters Add the consensus branch ID and activation heights to the consensus parameters #716
  • reimplement zcashconsensus in rust - reimplement zcash_script in rust #623

[hdevalence]

Duplicate of #196, merging.