 In contrast to the initial signature, the use of the hash of the contract within following transactions also signals intent, and forms a covert signature over the contract.Although private key signatures are well studied and are subject of legal frameworks such as the European digital signature directive, Grigg suggests that the trail of hashes - entanglement - forms a more effective evidence of intent  than a private key signature.As a pattern in design, the Ricardian Contract is like a reference - object tuple from the tradition of Object-oriented Programming.