Digital Signature

Why
Digital signatures are important because they allow us to provide data integrity and also they allow us to verify the sender

What
Digital signatures are applications of public key cryptosystems in which we use the private key to encrypt (sign) a message and people who receive the message use their public key against the signature to check if the message was from who they think it is from

Textbook Security Properties

 * Digital Signatures are secure if it is computationally infeasible for attackers to forge a valid message-signature pair from scratch. That is, when an attacker is given a public key and the description of a signature scheme and is required to produce a message-signature pair for which has never been issued by a targeted signer.
 * The attacker is non adaptive. That is, does not try to use previous message-signature pairs or to interact with the target signer and ask for valid signatures on messages of the attacker's choice

Types

 * RSA