Parse Orchard data in Transaction Version 5

[teor2345]

Is your feature request related to a problem?

Transaction version 5 contains Orchard data, which we need to parse:

• Design: https://github.com/ZcashFoundation/zebra/blob/main/book/src/dev/rfcs/0010-v5-transaction.md#orchard-additions
• Spec: https://zips.z.cash/protocol/nu5.pdf#txnencodingandconsensus

Describe the solution you'd like

Implementation

Flags

Documentation

• read the relevant consensus rules in the spec
• read the relevant RFC section
• summarise them in each struct and function's docs

implementation:

• Add orchard::Flags
  • https://github.com/ZcashFoundation/zebra/blob/main/book/src/dev/rfcs/0010-v5-transaction.md#adding-orchard-flags
• Implement serialization and deserialization for orchard::Flags according to the spec

Testing:

• Test round-trip serialization and deserialization for Arbitrary orchard::Flags

orchard module types

Implement serialization and deserialization if required:

• Action
• Halo2Proof
• redpallas::Signature<Binding>

AuthorizedAction

Documentation

• read the relevant RFC section
• summarise it in each struct and function's docs

Implementation:

• Add orchard::AuthorizedAction
  • https://github.com/ZcashFoundation/zebra/blob/main/book/src/dev/rfcs/0010-v5-transaction.md#adding-orchard-authorizedaction
• Implement trusted vector deserialization for Action, based on the size of AuthorizedAction
  • see the TrustedPreallocate impl for Output (V5) in https://github.com/oxarbitrage/zebra/pull/88/files#diff-f312291146990d763b96fd39ec0960937a0cb41678ff1ff3f5e9339011e1f376R195
  • replace Output with AuthorizedAction
  • replace OUTPUT_SIZE with AUTHORIZED_ACTION_SIZE
  • replace OutputPrefixInTransactionV5 with Action
  • replace OUTPUT_PREFIX_SIZE with ACTION_SIZE

Testing:

• Test Arbitrary AuthorizedAction trusted vector deserialization
  • see the preallocate.rs tests for output in https://github.com/oxarbitrage/zebra/pull/88/files#diff-a25350cfb4ab267dc20751f438c040e91f665bacaee28afcfa46b653c311189aR127
  • copy the v5 tests and change the types, ignore the v4 tests

ShieldedData

Documentation

• read the relevant consensus rules in the spec
• read the relevant RFC section
• summarise them in each struct and function's docs

Implementation:

• Add orchard::ShieldedData
  • https://github.com/ZcashFoundation/zebra/blob/main/book/src/dev/rfcs/0010-v5-transaction.md#adding-v5-transactions
  • https://github.com/ZcashFoundation/zebra/blob/main/book/src/dev/rfcs/0010-v5-transaction.md#adding-orchard-shieldeddata
• Delete the rest bytes field
• Implement serialization and deserialization for orchard::ShieldedData according to the spec

Testing:

• Test round-trip serialization and deserialization for Arbitrary orchard::ShieldedData

Transaction

Implementation:

• Implement serialization and deserialisation for the Transaction::V5 orchard fields using ShieldedData
• implement orchard_nullifiers
  • return empty orchard nullifiers for V1, V2, V3, and V4 Transactions
  • use an exhaustive version match, so we don't accidentally return empty nullifiers for V6

Test round-trip serialization and deserialisation for:

• Arbitrary transaction v5

Testing

High Priority

• Test round-trip serialization and deserialization for:
  • Transaction v5 test vectors from zcashd (or test vectors that we create and share with zcashd)
  • Orchard-only, Orchard/Sapling, Orchard/Transparent, and Orchard/Sapling/Transparent test vectors

Medium Priority

• Test round-trip serialization and deserialization for:
  • Arbitrary Action
    • the Action proptest might already be implemented
  • an empty transaction v5, with no Orchard, Sapling, or Transparent data
    • empty transaction are invalid, but Zebra only checks this rule in zebra_consensus::transaction::Verifier
  • large Orchard single-transaction-many-action and multi-transaction-single-action blocks, like: https://github.com/ZcashFoundation/zebra/blob/main/zebra-chain/src/block/tests/generate.rs#L18
    • also add them to the benchmarks, see Benchmark Block struct serialization code #2018

Describe alternatives you've considered

This is a required change for NU5. Alternative designs were considered during the RFC process.

Additional context

In #1829 we parsed the sapling data in transaction version 5.