A digital signature enables authentication of digital documents, text or data. It is used to prove that the author of the data is the expected one, and that the data has not been tampered with. To create a digital signature, public-key cryptography is used. Typically, a digital signature is created by first hashing the data to be signed into a 160-bit value, which is then encrypted using the unique Private Key held only by the party that is signing the data. Anyone holding the Public Key that corresponds to the Private Key can then use it to authenticate the author of the data and also to ensure that the data has not been altered since it was signed.