Symmetric cryptography is characterized by the fact that the same key is used both to encrypt plaintext (obtaining ciphertext as output) and to decipher the ciphertext (obtaining the original plaintext as output).
Asymmetric cryptography, on the other hand, is characterized by the introduction of two different keys, the public key and the private key, both associated by a mathematical relationship, which prevents or, at least, makes it very difficult in practice to trace back to the private key starting from the knowledge of the public key.
The two keys are therefore used to achieve different purposes: the public key is used to encrypt plaintext, while the corresponding private key is used to decipher the ciphertext.
Caesar's algorithm, which was introduced in the previous section, represents a very simple example of symmetric cryptography...