I would like to attribute my interest in cryptology to a specific event or book, but I cannot. If anything, I became interested in it when I wrote my detective novel “Walkürian” and had to come up with a handful of ciphers. In hindsight, it was a grave mistake to attempt devising encryption methods without first learning about the classics.
The story is always the same: the more unbreakable an amateur thinks their cipher is, the weaker it probably is. Luckily, I was spared the disgrace of having my ciphers decrypted by a pro. Therefore, I am going to share some of my amateurish encryption methods here because, according to Kerckhoff, the security of a cipher should be based on the key, not the lack of knowledge of the encryption method.
While I see the advantages of a cipher that can be solved with pen and paper, most of my methods relied on the computer from the start. Even the few manual methods I devised were first tested on the computer because it is faster and easier on the mind. None of my methods remotely approach the security associated with AES-256, our modern encryption standard, which is so robust that we will not need to invent a better one for the next couple of years. But some are fun nonetheless because they rely on real-world objects, such as card decks, the Rubik’s cube, or English dictionaries.
I also incorporated a bit of steganography, which is the art of hiding secret messages in plain sight. It is especially easy to conceal texts in uncompressed images because the latter are very data-intensive, whereas text messages require only a couple bytes.
Among my favorite encryption methods are: Vigenère, Doppelkastenschlüssel (double Playfair), Doppelwürfel (column rearrangement), and the Secure Hash Algorithm (SHA). I encourage you to read up on these in case you want to delve into cryptology yourself. By the way, ciphers are a great thing to teach your crush. You can use them to exchange short love notes or hide them around their place to brighten their day. Be sure to use a key they know.