[frontend] Make hash tweaking into a function

[paulcadman]

This PR changes the ChainTweak circuit from a struct:

pub struct ChainTweak {
  ... inout wires to be populated ...
}


impl ChainTweak {
  fn new(builder:: &CircuitBuilder, params) -> Self {
     ... build circuit ...
  }
}

To a function:

pub fn verify_chain_tweak(builder: &CircuitBuilder, params, ... inout wires ..., ) -> Keccak {
  ... build circuit ...
}

The populate_*functions are also removed, the caller is reponsible for populating the wires.

The function reutrns a Keccak verifier that must be populated with the expected digest and message.

A base verify_tweaked_keccak​ is also factored out which handles all tweaks of the form Keccak256(param || tweak || additional)​, this circuit will be used as a common function by all the tweaking circuits we need for hash-based signatures.

Note

Ideally the message wries would be passed in as an argument to the function, but there’s added complexity with this approach. The Keccak circuit contains a padded version of the message. This would have to be constructed and passed into the verify_chain_tweak​ function separately. So in this case it is arguable that it’s simpler to reuse the Keccak struct.

​

[paulcadman]

• [frontend] Add hash chain verification #808 : 3 dependent PRs (#809 , #810 , #820 )
• [frontend] Make hash tweaking into a function #819 👈 (View in Graphite)
• main

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Merge activity

• Sep 1, 3:16 PM UTC: paulcadman added this pull request to the Graphite merge queue.
• Sep 1, 3:16 PM UTC: CI is running for this pull request on a draft pull request (#897) due to your merge queue CI optimization settings.
• Sep 1, 3:22 PM UTC: Merged by the Graphite merge queue via draft PR: #897.