Detailed Analysis of encryption and decryption

Today has been encrypted and decrypted this piece made dizziness, because PKI also talked about this piece before, but passed by, today security also talked about this part, still did not understand, also talked to the teacher, the feeling is still not clear, always feel that the teacher did not understand what I mean, however, before dinner, I finally figured it out

1. Encryption and decryption of secret key

A B

Public key m 1 key n 1 public key m 2 key n 2

● when An encrypts with his own public key, no one can decipher the information but himself.

● when An and B transmit an encrypted message, for example, when A sends a message to B, A needs to encrypt it with B's public key. In this case, only B can unlock the message (highlighting encryption)

● when An is encrypted with its own private key, anyone with A's public key can decrypt the message. (authenticated)

two。 A question that you are confused about.

(pictured above) in itself, the public key cannot be derived, or it is very difficult to derive the key, but there is no doubt that the key can be derived from the public key.

However, on the issue of authentication, when An is encrypted with its own private key, all those who have the public key of A can decrypt the message, and when other users decrypt it, the public key of An is used for decryption. The question at this time is, isn't the public key unable to solve the private key?

At this point, the process of plaintext encryption is confused, because when authenticating, his public key is used to decrypt the ciphertext, this process is not to use the public key to deduce the public key, but to use the public key to decrypt the ciphertext.

Keep it in mind!