Digital signature is a method to authenticate digital information, which is similar to ordinary physical signature, but uses the technology in the field of public key encryption. A set of digital signatures usually defines two complementary operations, one for signing and the other for verification. Digital signature is a combination of asymmetric key encryption technology and public key encryption technology. In public key encryption technology, each user has a pair of keys: a public key and a private key. The public key can be released freely, but the private key is confidential. The signer encrypts the message with the private key, generates a specific signature value, and sends the signature value to the receiver together with the message. The receiver can use the sender's public key to decrypt and verify the signature value, thus determining the authenticity and integrity of the message.