ABSTRACT
As shown in Figure 2.1, symmetric-key cryptosystems require that
the two parties attempting to communicate share the same key.
This key is used for both encryption and decryption because the
two operations are symmetric, i.e. almost identical, hence why
such cryptosystems are known as symmetric-key cryptosystems.
Such cryptosystems are analogous to securing a cabinet with a
combination lock; anyone with the combination can either deposit
or withdraw information from the cabinet.
