In 1978, a new digital signature verification method called the RSA method was proposed, which can confirm the identity of the other user. The premise is that digital signatures can be generated by a public key system, and the premise is that the public key and the secret key are reciprocal, that is, if a plaintext message is "decrypted" with a certain secret key, Then the public key "encryption" can restore the message to plain text format, which is confidential communication.