Introduction to Classical Cryptography

In classical cryptography, we mainly introduce single-table alternative passwords, multi-table alternative passwords, and some other more interesting passwords.

It is worth mentioning that in classical cryptography, the designer mainly considers the confidentiality of the message, so that only the person with the relevant key can decrypt the ciphertext to obtain the content of the message, and the integrity and non-repudiation of the message are not carried out. Too many considerations.