Block Transposition Cipher
A block transposition cipher operates by rearranging groups of characters. A cipher can be categorized based on the type of operation it uses to convert a plain text message into a cipher-text message. There are two basic operations that a cipher can perform on a plain text message: substitute and transposition. A substitution cipher replaces the characters in a plain text message with different characters, whereas a transposition cipher only rearranges the order of the characters in a plain text message.