RGB state transition commitments

Multiple state transitions involving issuance and transfer of RGB can be incorporated into a single commitment. There are two ways to put the commitment into the Bitcoin transaction:

• Taproot commitment: an OP_RETURN script containing the LNPBP-4 message is involved in the top right leaf of the TapTree associated with the first Taproot output in the Bitcoin transaction. This information is disclosed exclusively off-chain to the recipient of the RGB transfer. Consequently, the Bitcoin transaction can include just one taproot output, serving dual purposes: sending the Bitcoin change back to the sender and embedding the commitment. This is achieved without any additional byte and without any indication that the Bitcoin transaction contains an RGB commitment.

• OP_RETURN commitment: the LNPBP-4 message is directly integrated into the first OP_RETURN output of the Bitcoin transaction. This adds an extra 46 bytes to the transaction. However, it does not disclose any details about the RGB transfer to blockchain observers, appearing merely as an OP_RETURN with a hash, like open timestamp transactions. The benefit of this method over the Taproot-based approach lies in its simplicity and the ease of implementation for wallet developers.

If a Bitcoin transaction contains several commitments, only the first one is pertinent to the RGB validation rules. Any additional commitments will be disregarded. This approach renders any efforts to double-spend ineffective.