Proposed penumbra-crypto code reorganization

[redshiftzero]

This is a more detailed proposal for the final item in #2288. As described there, penumbra-crypto has become a catch-all crate for a bunch of diverse functionality. The scope of this ticket is to:

1. Rehome the various modules of penumbra-crypto to existing crates that make sense, or create new crates if needed,
2. Remove code in penumbra-crypto we're not using, i.e. stuff that was originally targeted for Penumbra mainnet but will end up going into PenumbraV2, possibly with significant changes.

Concrete steps

Note that the following paths refer to the various modules in penumbra-crypto in crates/core/crypto.

• Move SwapFlow (in flow.rs) to the penumbra-dex component. Remove MockFlowCiphertext and instead just use Amounts. This removes flow.rs. - refactor: remove unused code in penumbra-crypto #2766
• Remove eddy.rs for now - we'll bring it back in the appropriate place if needed for PenumbraV2. - refactor: remove unused code in penumbra-crypto #2766
• Move code in governance* to the penumbra-governance crate. Currently this crate doesn't exist, so in the meantime we could move it alongside where the governance component lives. Then this governance code would all be moved together to the penumbra-governance crate, as described/tracked in Tracking issue: Modularize the Penumbra application code into coherent crates #2288. - refactor: move governance related items from crypto to governance crate #2776
• Move code in stake* to the penumbra-stake crate. - refactor: move penumbra-crypto staking-related types to staking crate  #2770
• Move memo.rs to the penumbra-transaction crate, since as of lift Memo to transaction level #1222 the memo is at the transaction level. - refactor: move memo to transaction crate #2773
• Move effect_hash.rs and transaction.rs to the penumbra-component crate (we need to implement EffectingHash for component-specific actions in the component crates). - an attempt in refactor: move effect hash struct/trait to penumbra-component #2779 that is failing CI, next attempt in refactor: move remaining code in penumbra-crypto to penumbra-chain #2798
• Create new crate penumbra-num for Amount and U128x128 types. - refactor: populate penumbra-num, penumbra-asset #2781
• Move asset* to a new penumbra-asset crate, along with Value and Balance - refactor: populate penumbra-num, penumbra-asset #2781
• Move note_payload.rs, rseed.rs, to penumbra-shielded-pool - refactor: move notes to penumbra-shielded-pool, nullifiers to penumbra-sct #2795
• For the proofs, we'll move each of the proofs to the appropriate component crate, as was already done for the SwapProof and SwapClaimProof. Specifically:
  • UndelegateClaim goes to penumbra-stake, - refactor: move undelegate claim proof and circuit to stake crate #2769
  • Output, Spend, NullifierDerivation goes to penumbra-shielded-pool, - refactor: move remainder of ZKPs out from penumbra-crypto #2792
  • DelegatorVote goes to penumbra-governance - refactor: move remainder of ZKPs out from penumbra-crypto #2792
• The proof traits should go into penumbra-proof-params. The traits are used by the component crates, which already require the penumbra-proof-params to do proving and verification. - refactor: move remainder of ZKPs out from penumbra-crypto #2792
• Create new crate penumbra-fee for the Fee type #2774
• nullifier.rs would move to the penumbra-sct crate. - refactor: move notes to penumbra-shielded-pool, nullifiers to penumbra-sct #2795
• Create new crate penumbra-keys for the key hierarchy (keys*), addresses (address*), prf.rs (used for key derivation, and also by Rseed so we'd need to expose it), this requires some API changes: refactor: move keys and addresses modules into penumbra-keys #2791
• Move symmetric keys to penumbra-keys - symmetric.rs operates on notes and memos, might need API changes here - refactor: move notes to penumbra-shielded-pool, nullifiers to penumbra-sct #2795
• At this point, penumbra-crypto should be empty, so we'd delete it. As a final step, the re-exported types Fr, Fq and rdsa will need to be imported directly from decaf377 and decaf377-rdsa. - refactor: move remaining code in penumbra-crypto to penumbra-chain #2798

[conorsch]

Ticket still open to track cleanup, but we've largely achieved the reorg we wanted in advance of pending security audits. 🎉