Feat/eip4844 precompile

[ThomasPiellard]

Description

Implementation of the EIP4844 precompile.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How has this been tested?

See marshall_test.go, kzg_point_evaluation_test.go

How has this been benchmarked?

Unmarshall #constraints: 1772 when compiled on BN254, emulating BLS12-381 base field
UnmarshalCompressed #constraints: 585600 when compiled on BN254, emulating BLS12-381 base field
KzgPointEvaluation #constraints: 3772424 when compiled on BN254, emulating BLS12-381 base field

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I did not modify files generated from templates
• golangci-lint does not output errors locally
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[cursor]

Bug: KZG Precompile Hash Size Mismatch

The KZG point evaluation precompile's versioned hash verification contains an array out-of-bounds error. sizeCompressedPoint is incorrectly set to 48 bytes (fp.Bytes), while the EIP-4844 versioned hash is a 32-byte SHA256 output. This causes h.FixedLengthSum to produce a 48-byte hash. The subsequent comparison loop iterates up to 47, attempting to access versionnedHash beyond its 32-byte length, leading to an out-of-bounds panic.

std/evmprecompiles/10-kzg_point_evaluation.go#L63-L74

gnark/std/evmprecompiles/10-kzg_point_evaluation.go

Lines 63 to 74 in 7c23ab0

	// verify commitment matches versioned_hash
	sizeCompressedPoint := fp.Bytes
	h, err := sha2.New(api, hash.WithMinimalLength(sizeCompressedPoint))
	if err != nil {
	return nil, fmt.Errorf("new sha2: %w", err)
	}
	h.Write(comSerialised)
	hashedKzg := h.FixedLengthSum(sizeCompressedPoint)
	api.AssertIsEqual(versionnedHash[0].Val, blobCommitmentVersionKZG)
	for i := 1; i < len(hashedKzg); i++ {
	api.AssertIsEqual(hashedKzg[i].Val, versionnedHash[i].Val)
	}

Fix in Cursor

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