Learn in the textbookFundamentals of Encryption and Cipher Methods
DefinitionPublic-key cryptography (公開鍵暗号方式) uses a pair of keys, a public key (公開鍵) that can be given to anyone and a private key (秘密鍵) held only by its owner, and data encrypted with one is decrypted with the other.
ExplanationThe public and private keys are generated as a mathematically linked pair, and working out the private key from the public key is practically impossible. The private key never leaves the person who created it, and only the public key is given to others. RSA is a typical example.
AnalogyIt is like handing out many padlocks that anyone can snap shut while keeping the only key yourself. When someone locks a box with one of them and sends it to you, only you can open it.
Memory hookIt is also called asymmetric cryptography: the encryption key and the decryption key do not mirror each other, so they are different keys.