NonMembership proof

[dai1975]

Change prover and verifier to use NonMembership proof when value is null

[Copilot]

Pull Request Overview

This PR updates the prover and verifier implementations to use NonMembership proofs when provided with a null value.

• In relay/prover.go, a new branch handles empty value cases by invoking VerifyNonMembership instead of VerifyMembership.
• In light-clients/lcp/types/client_state.go, the verification logic is modified to only compute and compare the hash when the value is non-empty.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
relay/prover.go	Adds NonMembership proof handling for empty values and updates the proof decoding pipeline.
light-clients/lcp/types/client_state.go	Skips computing the hash for empty values during membership verification.

Comments suppressed due to low confidence (1)

relay/prover.go:345

• [nitpick] The variable name 'cp' is ambiguous. Consider renaming it to 'commitmentProofs' to improve clarity.

var cp lcptypes.CommitmentProofs

[Copilot]

Pull Request Overview

This PR updates the logic for state proof verification to use a NonMembership proof when the provided value is empty.

• In relay/prover.go, a new branch handles NonMembership proofs using elc.MsgVerifyNonMembership when value is null.
• In light-clients/lcp/types/client_state.go, the code now computes the hashed value only when a value is provided during membership verification.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
relay/prover.go	Added a new branch to request a NonMembership proof when the input value is empty.
light-clients/lcp/types/client_state.go	Updated the value hashing logic to only execute for non-empty values, aligning with NonMembership proofs.

[Copilot]

[nitpick] Both the NonMembership and Membership branches assign cp.Message and cp.Signatures in an identical manner. Consider refactoring to reduce code duplication by extracting these assignments outside the conditional branches.

Suggested change

	res, err := pr.lcpServiceClient.VerifyNonMembership(ctx.Context(), &m)
	if err != nil {
	return nil, clienttypes.Height{}, fmt.Errorf("failed ELC's VerifyNonMembership: elc_client_id=%v msg=%v %w", pr.config.ElcClientId, m, err)
	}
	cp.Message = res.Message
	cp.Signatures = [][]byte{res.Signature}
	var err error
	res, err = pr.lcpServiceClient.VerifyNonMembership(ctx.Context(), &m)
	if err != nil {
	return nil, clienttypes.Height{}, fmt.Errorf("failed ELC's VerifyNonMembership: elc_client_id=%v msg=%v %w", pr.config.ElcClientId, m, err)
	}

[dai1975]

The return type of VerifyMembership and VerifyMembership is not compatible.
I think generics is needed to commonalize these code, it is a bit over spec at this situation.

[Copilot]

Pull Request Overview

This PR modifies the prover and verifier logic to use NonMembership proofs when the provided value is null.

• In relay/prover.go, a branch is added to call VerifyNonMembership and assign the corresponding proof and signature when value is empty.
• In light-clients/lcp/types/client_state.go, the hash computation is conditioned on the value being non-empty to support NonMembership logic.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
relay/prover.go	Added NonMembership branch and adjusted proof encoding for empty values.
light-clients/lcp/types/client_state.go	Modified hash computation logic to conditionally handle empty values for non-membership.

Comments suppressed due to low confidence (2)

relay/prover.go:386

• [nitpick] Consider renaming 'cpEnc' to 'encodedProofs' or another more descriptive name to improve clarity.

cpEnc, err := lcptypes.EthABIEncodeCommitmentProofs(&cp)

light-clients/lcp/types/client_state.go:236

• Ensure that there are unit tests covering both the membership and non-membership verification paths, as the new conditional logic impacts how the hashed value is computed.

hashedValue := crypto.Keccak256Hash(value)