How does Public Key Encryption work?

Answer 1

The exact mathematics of the encryption differ depending on the algorithm used, but in principle, this is how it works.

An algorithm is used to generate a pair of keys that are related mathematically. In many cases they are factors of a very large number. One of the keys is the Public key, which is published to a key registry. The other is the Private key which is held by the owner alone. The important thing is that it is supposed to be impossible to derive the Private key from the Public key. When the owner wants to send a message, the use the Private key to encrypt it or to sign it. Since only the corresponding Public key can decrypt it, that establishes that the sender is who they say they are (because only they should have the Private key). If the sender used their Private key to sign the message, the receiver can use the Public key verify that the message has not been tampered with. On the flip side, some can encrypt a message to the owner of the Private key by using that person's Public key. Only the holder of the Private key can decrypt the message. This can provide confidentiality. Two correspondents can establish secure communications by using each others Public keys to encrypt their messages.

Often the public key is deposited with a trusted Certificate Authority. Assuming the user trusts the key repository, they can use them to authenticate the key they are using as belonging to the person it is supposed to belong to.

To get more details on the mathematics of encryption and decrption using Public Key

Encryption, aka asymmetric encryption. Do a web search for the particular algorithm involved, be it SSH, PGP, TLS, or some other protocol.

Answer 2

In public key cryptography there are two parts: 1) secret part 2) public part ,in order for p1 to send p2 a message ,p1 first need to obtain p2's public key and using this key encrypts the message then p2 using his secret key decrypts the message. And in private key cryptograhy there is only one key so in order for p1 to send a message to p2, p1 should firstly ask p2 for his key then encrypt the message using that key and then p2 uses the same key to decrypt the message.

Answer 3

In public key cryptography there are two parts: 1) secret part 2) public part in order for p1 to send p2 a message ,p1 first need to obtain p2's public key and using this key encrypts the message then p2 using his secret key decrypts the message.