how does public key cryptography work [duplicate]

Answer 1

Basically, the procedure is:

1. The client connects to the server and asks for the server's certificate. The certificate contains the public key and information about the server's identity.
2. Assuming the client is happy with the server's identity, it generates a random number P and encrypts it with the server's public key.
3. Only the server can decrypt P (with it's private key - not shared with anybody) so when the client sends the encrypted random number to the server, the server decrypts it.
4. The client and server both use P to generate a symmetric key for use in a symmetric encryption algorithm, safe in the knowledge that only the client and server know the value of P used to generate the key.