Investigate using blake2s logic from `types-rs` repo

[gabrielbosio]

Investigate if the VM can use the blake2s functions defined in types-rs to simplify codebase.

We need to check if the behavior and performance of the vm does not change.

Links:

• Implementation in types-rs
• Logic from the VM that may use types-rs

[JulianGCalderon]

The current types-rs API does not work for our use case. Currently, it exposes:

pub fn blake2s_to_felt(data: &[u8]) -> Felt;

It hashes all the data at once, which is not what we need.

From the Cairo VM (and also in Cairo Native), we need a much low-level API for Blake2. We would need something like this:

pub fn blake2s_compress(
    state: &[u32; 8],
    message: &[u32; 16],
    t0: u32,
    t1: u32, // optional? always zero.
    f0: u32,
    f1: u32, // optional? always zero.
) -> [u32; 8];

As this API requires the user to know the initial state, we also also need a way to obtain either the IV, or the initial state.

pub fn get_initial_state() -> [u32; 8]; // or
pub fn get_iv() -> [u32; 8];

The Rust crate blake2 does not expose this functionality, so we would need to implement it manually. See blake2s_hash.rs.

In addition to the mentioned functions, the following utilities would come in handy:

pub fn encode_u128s_to_u32s_le(numbers: &[u128]) -> Vec<u32>;
pub fn encode_u128s_to_u32s_be(numbers: &[u128]) -> Vec<u32>;

The following utilities are already implemented, and can be used:

pub fn encode_felts_to_u32s(felts: &[Felt]) -> Vec<u32>;
pub fn pack_256_le_to_felt(bytes: &[u8]) -> Felt;

[gabrielbosio]

Moving blake2s logic from the VM to types-rs implies removing the blake2s_compress function which is public and not intended to be removed in the next releases.