Epic: Addresses & Keys Changes

[iAmMichaelConnor]

Following several rounds of discussions and decisions, here's a list of tasks relating to changes to addresses & keys.

New address scheme

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1. Implement the new address scheme across the stack #9326
   C-aztec.js C-aztec.nr C-protocol-circuits team-fairies +4
   
2. Change the aztec-nr Address derivation #8966
   C-aztec.nr team-fairies +2
   
3. Consider removing the PXE 'registerRecipient' API #9646
   C-pxe team-fairies +2
   

Keys

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1. Remove code relating to key rotation
2. Remove the key registry
3. Send notes using Addresses instead of keys #8969
   C-aztec.nr C-pxe team-fairies +3
   
4. Remove npk_m_hash from notes and replace with address #9648
   C-aztec.nr team-fairies +2
   
5. Don't app-silo outgoing viewing keys anymore #9162
   C-aztec.nr team-fairies +2
6. Handle invalid Addresses #8970
   C-aztec.nr team-fairies +2
7. Derive a note's randomness from the ephemeral shared secret. #8999
   C-aztec.nr C-pxe team-fairies +3
8. P1: Internal Incoming Viewing Keys

p1: Plume

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1. Liaise w/ Crypto Research to ensure security of approach for Plume w/ Grumpkin & Posiedon2 [Mike to do]
2. Run the latest flamegraph of the reset private kernel circuit, to determine the constraint counts for one key validation request. Compare it against 3300 for plume.
3. Implement an example flow of using plume nullifiers.
4. Fun: Explore how to add Grumpkin ops as an 'app' on Ledger hardware wallets.
5. Example Escrow contract

[nventuro]

The key registry was removed in #8613, and key rotation was then fully removed in #8645.

[rahul-kothari]

Marking plume and internal incoming keys as p1 (i.e. post testnet)

[sklppy88]

#9326, #8966, #8969 are resolved by the stack at #9272, with some enhancements in later PRs in the stack.

[sklppy88]

After replacing npk_m_h with address in #9461, we can send notes to users without their public keys !

This means registerRecipient is unnecessary now, and was nuked in #9548.

I think this concludes P0 tasks here with the full initial implementation of the new address and keys changes ?