Correct digital signature (also known as public key digital signature and electronic signature) is an ordinary physical signature, similar to the signature written on paper, but it is realized by using the technology in the field of public key encryption to identify digital information. A set of digital signatures usually defines two complementary operations, one for signing and the other for verification. A digital signature is a digital string, which can only be generated by the sender of the information, and no one else can forge it. This number string is also an effective proof of the authenticity of the information sent by the information sender. Digital signature is the application of asymmetric key encryption technology and digital digest technology. The integrity of digitally signed documents is easy to verify (no need for printing, signing or handwriting experts), and digital signatures are undeniable (no need for handwriting experts to verify). Simply put, the so-called digital signature is some data attached to the data unit, or the cryptographic transformation of the data unit. This kind of data or transformation allows the receiver of the data unit to confirm the source and integrity of the data unit and protect the data from being forged by people (such as the receiver). This is a method of signing an electronic message, and the signed message can be transmitted in a communication network. Digital signature can be obtained based on both public key cryptosystem and private key cryptosystem, mainly digital signature based on public key cryptosystem. Include general digital signature and special digital signature. Common digital signature algorithms include RSA, ElGamal, Fiat-Shamir, Guillou-Quisqour, Schnorr, Ong-Schnorr-Shamir, Des/DSA, elliptic curve digital signature algorithm and finite automaton digital signature algorithm. Special digital signatures include blind signature, proxy signature, group signature, undeniable signature, fair blind signature, threshold signature, signature with message recovery function and so on. It is closely related to the specific application environment. Obviously, the application of digital signature involves legal issues, and the federal government of the United States has formulated its own digital signature standard (DSS) based on the discrete logarithm problem over a finite field.