The Vigenère Cipher is a classical cryptographic method that enhances the security of simple substitution ciphers. It was developed by the French diplomat Blaise de Vigenère in the 16th century.

The Vernam Cipher, also known as the "One-Time Pad," is a powerful and unbreakable encryption technique known for its exceptional security when used correctly. It falls under the category of symmetric encryption, where both the sender and recipient share the same secret key.

A Transposition Cipher is a type of cryptographic method that encrypts messages by rearranging the characters or symbols of the plaintext without altering the original letters themselves. Instead of replacing letters with different symbols (as in substitution ciphers), transposition ciphers focus on changing the order of the characters to conceal the message.

Tap Codes are a clever and secretive way of communicating using a series of taps or knocks. This form of communication was devised to facilitate discreet messaging, especially in situations where speaking aloud is not an option or could be overheard.

In the T9 system, each digit key on the phone keypad corresponds to a set of letters. By pressing the keys multiple times, you cycle through the letters associated with each key. The mapping of letters to the keypad digits is based on the arrangement of letters on a standard telephone keypad:

The Spiral Cipher is a method of encrypting messages by arranging the plaintext in a spiral pattern, typically on a grid or matrix. It is a type of transposition cipher, where the original letters of the message are preserved but rearranged in a specific order.