Applications
- Encryption with public key, decryption with private key
- Confidentiality or secrecy
- Encryption with private key, decryption with public key
- Integrity/authentication
Clarification of some conceptual features:
public key: everyone knows (public information)
private key: only the owner knows
Confidentiality or secrecy
Encryption with public key, decryption with private key
When B transmits a confidential file to A, it needs to use A's public key (public information) for encryption, because only A knows its own private key (only the owner knows it).
When B transmits confidential files to people in a class, he needs to use the public key corresponding to each person (A) to encrypt each time, and send it to the corresponding person (A), and the corresponding person (A) can use his own private key to decrypt it.
Integrity/authentication
Encryption with private key, decryption with public key
B uses a private key to encrypt information, and the private key here can only be B's own private key. Everyone else can decrypt the information (because B's public key is public information).
The meaning of this is: other people can determine that this is a message sent by B (authentication).