Caesar Shift
The Caesar Shift is a type of substitution cipher originally used by Julius Caesar to protect messages of military significance. It shifts letters in the alphabet left or right by a specified number (the shift number). The shift number must be between -25 and 25. To decode, you are required to know the shift number.
Polybius Square
The Polybius Square is a cipher that is achieved by arranging a typical alphabet into a grid. Each letter is represented through a coordinate. For example, the letter "B" is represented by the numerical pair "21".
Substitution Cipher
Uses a standard and a substitution alphabet. Letters from the standard are replaced by those in the substitution. For example, if "A" in the standard becomes "K" in the substitution, then "A" in the message becomes "K". To decode, have the substitution alphabet.