feat!: Add variable length keccak opcode

[kevaundray]

Related issue(s)

(If it does not already exist, first create a GitHub issue that describes the problem this Pull Request (PR) solves before creating the PR and link it here.)

Resolves #313

Description

Summary of changes

(Describe the changes in this PR. Point out breaking changes if any.)

Dependency additions / changes

(If applicable.)

Test additions / changes

(If applicable.)

Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt with default settings.
• I have linked this PR to the issue(s) that it resolves.
• I have reviewed the changes on GitHub, line by line.
• I have ensured all changes are covered in the description.

Additional context

(If applicable.)

[TomAFrench]

Do we need to have two variants here? What are the benefits of this compared to just having the variable version and passing in msg.len() for the fixed size keccak?

[kevaundray]

Do we need to have two variants here? What are the benefits of this compared to just having the variable version and passing in msg.len() for the fixed size keccak?

They have different implementations on the backend, so if we put the msg.len() parameter on Keccak, then backends will need to implement KeccakVar which is harder to implement than Keccak.

Theres also the fact that regular Keccak is more performant when var_message_size is a constant, I don't know how much more performant it is though

[TomAFrench]

Ok cool, this looks sensible if we're going down the two opcodes route.

Shall we add a todo to add variable variants of the other hash functions?

[kevaundray]

Ok cool, this looks sensible if we're going down the two opcodes route.

Shall we add a todo to add variable variants of the other hash functions?

Yep sure, made #320