Codes and Ciphers

Description
During a casual conversation, the words 'code' and 'cipher' are usually interchangeable. Both refer to methods of encrypting text that must be deciphered to understand the real meaning of the text, often story information or a clue for the next puzzle. This is the most common form of puzzle found in ARG's. They can often be broken with decoder websites (see below). Some may be instantly decoded, while others may require a password or key.

Cryptii
A popular decoding website with many common codes and ciphers with an easy to use UI.

DCode
Another popular decoding website with common codes and ciphers, as well as many lesser known or incredibly obscure ones as well. It has a harder to use UI, but it has a much wider selection, alongside wiki pages describing different codes & ciphers, how they work, and how to use them. An immensely useful resource.

Boxentriq
A website dedicated to codes, ciphers, and puzzle games. They have a section about codes and ciphers, with encoders/decoders and easy to understand information about many common (and some uncommon) codes and ciphers.

Morse Code
Morse code assigns a unique combination of signal made of short and long impulsions (usually represented with a dot " ." and a dash " -" ) to each letter, digit, or punctuation sign.

Vigenere Cipher
In the Vigenère cipher, a message is encrypted using a secret key, as well as an encryption table (called a Vigenere square, Vigenere table. The tablw recta typically contains the 26 letters of the Latin alphabet from A to Z along the top of each column, and repeated along the left side at the beginning of each row. Each row of the square has the 26 letters of the Latin alphabet, shifted one position to the right in a cyclic way as the rows progress downwards. Once B moves to the front, A moves down to the end. This continues for the entire square.

Caesar Cipher
Consists of each letter being replaced by another letter located a little further in the alphabet (therefore shifted but always the same for given cipher message). The shift distance is chosen by a number called the offset. For example, a shift of 3 would turn the letter "A" into the letter "D".

A1Z26
Consists of replacing each letter by its position in the alphabet, for example A=1, B=2, Z=26, hence its over name A1Z26.

Enigma Machine
A cipher originally invented in the 1920's and cracked during WW2. Uses a series of rotating letters (rotors) in conjunction with reflectors and a plugboard that swaps letters around. Incredibly complex, as the settings for all of these elements must be known in order to decrypt it.

Polybius Cipher
Polybius square uses a 5x5 grid filled with letters for encryption. Since the alphabet has 26 letters and the grid has 25 cells, a letter to remove is chosen, usually it's J, V , W or Z which are deleted. A key word is typically written in the first boxes in the grid, and the rest of the alphabet (minus the letters used in the key word) take up the following boxes.

Monoalphabetic Substitution Cipher
The monoalphabetical substitution consists in using a mixed alphabet (with the letters in an unusual order) and replacing the letters of the alphabet normal by it. To use this cipher, you will need to create your own scrambled alphabet (called a deranged alphabet) in order to tell the cipher how to shuffle the letters in your message. You can generate a deranged alphabet here.

Atbash Cipher
Atbash cipher (also called  mirror cipher  or  backwards alphabet  or  reverse alphabet ) uses a substitution alphabet and its reciprocal [reverse], a combination of the normal alphabet (ABCDEFGHIJKLMNOPQRSTUVWXYZ) and its reverse alphabet (ZYXWVUTSRQPONMLKJIHGFEDCBA).

Base64
Base 64 encoding requires a binary input. For a text, the values depend on its coding (often ASCII or Unicode). This cipher is commonly thought of as overused, unfun, and too easy by the ARG community.

Binary Code
Associates combinations of the numbers '1' and '0' with each letter of the alphabet a number. This will replace each letter by a number that can then be converted to binary. This is a type of computer language which consists of an arithmetic base conversion from base 10 to base 2. This cipher is commonly thought of as overused, unfun, and too easy by the ARG community.