A digital signature is a number that is transmitted with an electronic message to identify the sender. Depending upon the method implemented in a given system, the user may not even know the number added to the message. The digital signature is a pair of large numbers represented in a computer as strings of binary digits. The digital signature is computed using a set of rules and a set of parameters such that it can be used to verify the identity of the originator and integrity of the data. The digital signature includes signature generation and verification.
Generation makes use of a private key to generate a digital signature.
Verification of the signature makes use of a public key which corresponds to, but is not the same as, the private key used to generate the signature. The two keys are mathematically related, but the private key cannot be determined from the public key. The private key is kept secret. Its use should be controlled by its owner and it should be protected against modification as well as disclosure. Each user possesses a private and public key pair.