The integrity of digital signature documents is easy to verify (no experts in printing, signing or handwriting are needed), and the digital signature is undeniable. ? Everyone has a pair of "keys" (digital identities), one of which is known only by her/him (private key) and the other is public key (public key). Use the private key when signing and the public key when verifying the signature. And because anyone can claim that she/he is you, the public key must be registered with the person (certification authority) that the receiver trusts. After registration, the authentication institution will issue you a digital certificate. After signing the document, you send this digital certificate to the receiver together with the document and signature, and the receiver asks the authentication institution whether it is really a document signed with your key.

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 protects 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.