Digital signature on file using biometric fingerprint with fingerprint sensor on smartphone

Digital signature is a term that use a key pair of user for sign and verify a document. People can create their digital signature using biometric technology. Biometric technology is a concept that allows people to doing an digitally authentication using their bodies, for example by using their fingerprint. Now, fingerprint biometric technology system was available in some smartphone product, so that allows user to unlocking their smartphone only by scanning their fingerprint into smartphone's fingerprint sensor. The combination of that's all technology (digital signature, biometric fingerprint, smartphone with fingerprint sensor) can arise an innovation to make a system that can create a digital signature only using fingerprint on smartphone. This system applied to a method of signing document digitally. When user sending a document to other, user who send the document have to put their fingerprint into smartphone fingerprint sensor and the the document will be encrypted. Then, user who receive the encrypted message will decrypt the message using public key of user who as a sender. In this case, fingerprint is a medium to call the value of user private key from the database. Key pair algorithm for this system is using RSA algorithm.