If we think of encryption as playing table tennis where each person has just one bat and the pace is extremely fast, this is similar to asymmetric encryption as it uses one key.
Then, if we change the game and we give the players two bats – the first bat to stop the ball and the second bat to turn the ball – this would be much slower.
The same can be said for encryption; asymmetric encryption is much more secure as it has two keys and uses DH, an asymmetric technique for setting up a secure tunnel for the symmetric data. Symmetric encryption uses a block cipher and encrypts large blocks of data much faster than the asymmetric technique.
