What is Digital signatures
A major benefit of public key cryptography is that it provides a method for employing digital signatures. Digital signatures let the recipient of information verify the authenticity of the information’s origin, and also verify that the information was not altered while in transit. Thus, public key digital signatures provide authentication and data integrity. These features are every bit as fundamental to cryptography as privacy, if not more.
A digital signature serves the same purpose as a seal on a document, or a hand-written signature. However, because of the way it is created, it is superior to a seal or signature in an important way. A digital signature not only attests to the identity of the signer, but it also shows that the contents of the information signed has not been modified.
A physical seal or handwritten signature cannot do that. However, like a physical seal that can be created by anyone with possession of the signet, a digital signature can be created by anyone with the private key of that signing key-pair.