The electronic signature comes from the need for companies and administration to reduce costs and increase the security of their internal processes.
One of the methods of the electronic signature is the written electronic signature which consists of the capture of a physical signature by means of a signature device, known as a signature pad.
You need the appropriate hardware and software in order to carry out the written electronic signature.
An effective algorithm has to make use of a public key system to encrypt only the signature. Specifically, the “hash” value will encrypt, by using the private key of the signer, in such a way that anyone can verify the signature using the corresponding public key. The signed document could be sent using any other encrypting algorithm, or even none if it is a public document. In the event that the document is modified, the verification of the signature will fail, but this is precisely what the verification is supposed to discover.
Here you can find further information about the electronic signatur.