Analysis: There are two systems for encrypting/decrypting information, one is a single-key system or a symmetric encryption system (such as DES), and the other is a double-key system or an asymmetric encryption system (such as RSA). Digital signature generally adopts asymmetric encryption technology (such as RSA): a value is obtained by transforming the signature object (called plaintext), and the sender encrypts the value with his own key to form a signature and attach it to plaintext for transmission to the receiver; The receiver decrypts the signature using the sender's public key and performs the same transformation on the plaintext. If the value is consistent with the decryption result, the signature is valid, which proves that this article is indeed sent by the corresponding sender. Of course, the signature can also be used in other ways to confirm that the receiver did receive the message.