Optimizations: Equihash & Feats: Assumevalid + SPV

[b-j-roberts]

Summary

Optimizes the Equihash proof-of-work validation for ZK prover efficiency. Restructures validation to minimize Cairo steps while maintaining full security guarantees equivalent to the reference implementation.

Current savings estimate: 40,277,059 steps -> 859,899 steps ( ~98% )

Key Optimizations/Changes

• Blake2b cairo1 implementation -> Blake2b opcode: Enabled via blake2b feature flag, so cairo1 impl is used by default
• Blake2b Base Hasher Caching: Pre-computes first compression block (128 bytes of 140-byte header) once, clones for each of 512 leaf hashes
• U32-Optimized Nodes: Stores 20-bit collision elements as Array<u32> instead of Array<u8>, eliminating expand_array byte manipulation
• O(n) Uniqueness Check: Replaces O(n²) pairwise distinct_indices with Schwartz-Zippel permutation verification using prover-provided sorted hint
• Reduced intermediate byte arrays, type conversions, and redundant parsing/checks throughout the equihash implementation

How to Test

Using cairo1 blake2b

   cd packages/client
   ../../scripts/data/integration_tests.sh

Using blake2b opcode

1. Clone & build zoro-proving-stack ( See zoro-proving-stack for more info )

git clone --recursive https://github.com/Ztarknet/zoro-proving-stack.git
cd zoro-proving-stack
./setup.sh

make scarb-build

2. Run the test with custom scarb version

   cd packages/client
   SCARB=/path/to/scarb/target/debug/scarb ../../scripts/data/integration_tests.sh --features=blake2b

[m-kus]

Would need to change that in the assumevalid crate as well (preparing args)