Electronic signature is an electronic technical means, which can identify the true identities of both parties in electronic documents, ensure the security, authenticity and inertia of transactions, and play the same role as handwritten signature or seal.

It is different from the concept of digital signature. The so-called "digital signature" is to generate a series of symbols and codes through some cryptographic operation to form an electronic password for signature, rather than writing a signature or seal. At present, the signature technology widely used in the world is "digital signature" technology, that is, public key cryptosystem, but it is not the only technology. The signature mentioned in the current electronic signature law generally refers to "digital signature".

After making clear the concepts of digital signature and electronic signature, we will understand how digital signature is used and how to achieve the effect of tamper prevention. Now simply use the public key algorithm system to introduce the application process of digital signature.

It mainly includes two processes: signature and signature verification, which can actually be understood as encryption and decryption.

First of all, the signature needs a digital code to uniquely identify a person or entity, which requires the use of key pairs, one encryption and one decryption. Encrypt information with the sender's private key and then decrypt it with the public key. If it can be decrypted, it means that the sender sent this information encrypted, otherwise the sender's private key will no longer be kept secret.

For example, A wants to send a file to B, provided that both A and B have a pair of keys (public key and private key). The file to be sent is calculated by hash function to get a digital digest (characteristic: one-way, fixed length), then the digital digest is encrypted with A's private key to get a signature value, and the signature value and plaintext are passed to B. After receiving the digital signature, B decrypts the signature value with A's public key to get a new digital digest, and hashes the received plaintext to get a digital digest, and compares the decrypted digital digest with the digital digest obtained by hash operation. if