Validity rule for MessageShareCommitments to be sorted by square size

[rootulp]

Context

• Validate all relevant square sizes are committed to in MsgWirePayForData #666 (comment)

Problem

The message share commitments in a WirePayForData aren't sorted in a particular order so validators must sort them in order to determine if all relevant square sizes have been signed over.

Proposal

Add a new validity rule that states: "message share commitments must be sorted in ascending square size order"

Links

• https://celestiaorg.github.io/celestia-specs/latest/specs/data_structures.html?highlight=MessageShare#signedtransactiondatapayformessage

[rootulp]

This issue likely includes updating the MessageShareCommitment from HashDigest to more closely match the current implementation:

celestia-app/proto/payment/tx.proto

Lines 32 to 37 in b75f6be

	// ShareCommitAndSignature defines the
	message ShareCommitAndSignature {
	uint64 k = 1;
	bytes share_commitment = 2;
	bytes signature = 3; // signature on one SignedTransactionPayForData
	}

Screenshot

[adlerjohn]

If we're allowing the WireMayForMessage to be non-exhaustive w.r.t. k, then yes.

[rootulp]

This validity rule is no longer necessary if we adopt #835

[rootulp]

Closed b/c we assumed we're adopting #835