 Deciphering is done in reverse, with a right shift of 3.The encryption can also be represented using modular arithmetic by first transforming the letters into numbers, according to the scheme, A → 0, B → 1, ..., Z → 25.Encryption of a letter "x" by a shift "n" can be described mathematically as,

Decryption is performed similarly,

The replacement remains the same throughout the message, so the cipher is classed as a type of "monoalphabetic substitution", as opposed to "polyalphabetic substitution".