Digital signature

A digital signature is a mathematical scheme for verifying the authenticity of digital messages or documents. A valid digital signature on a message gives any recipient confidence that the message came from a sender known to the recipient. In contrast, a message authentication code only gives confidence to a specific recipient that the message came from a known sender.

Digital signatures are a type of public-key cryptography, and are commonly used for software distribution,

financial transactions, contract management software, and in other cases where it is important to detect forgery or tampering.

A digital signature on a message or document is similar to a handwritten signature on paper, but it is not restricted to a physical medium like paper—any bitstring can be digitally signed—and while a handwritten signature on paper could be copied onto other paper in a forgery, a digital signature on a message is mathematically bound to the content of the message so that it is infeasible for anyone to forge a valid digital signature on any other message.

Digital signatures are often used to implement electronic signatures, which include any electronic data that carries the intent of a signature, but not all electronic signatures use digital signatures.

Definition

A digital signature scheme consists of three algorithms:

A key generation algorithm that selects a private key at random from a set of possible private keys. The algorithm outputs the private key and a corresponding public key.

A signing algorithm that, given a message and a private key, produces a signature.

A signature verifying algorithm that, given the message, public key and signature, either accepts or rejects the message's claim to authenticity.