A new development in encryption technology is the ability to encrypt an electronic signature. If the sender uses the recipient’s public key to encrypt the message, once encrypted, only the private key can decrypt this message, because it is the only one who knows. Therefore confidentiality is achieved by sending the message, no one but the recipient can decrypt it. If the key pair owner uses his private key to encrypt the message, anyone can decrypt it using your public key. In this case we get the identification and authentication sender, since it is known that only could have been he who used his private key (unless someone could have stolen it). This idea is the foundation of electronic signatures. It is the certified electronic signature gives the document its legal value as eg an electronically signed invoice.
Law 59/2003 on electronic signatures matched, legally, the electronic signature to the signature on paper, thus giving it legal validity of electronic transactions for public and private, and Royal Decree 1496/2003 of 28 November determining the possibility to transmit invoices electronically. If you have the public key certificate of the electronic signature can verify that the invoice is actually sent from the sender. In addition, you can not modify a signed invoice electronically without altering the encryption and invalidate the bill. Therefore, it is the safest way to send and receive invoices, without coming here other advantages of the electronic invoice, such as cost savings same management and flexibility is to have a bill whose information can be exploited in many different ways in our business processes.