ABSTRACT
The most famous cryptographic device ever used was the German Enigma machine during World War II. Cryptography is the study of techniques for disguising messages so that ideally only the intended recipient of a message can remove the disguise and read the message. Such techniques are called ciphers. One very simple type of cipher involves replacing every occurrence of each specific character in a message with a different specific character, yielding what is called a substitutioncipher. The chapter shows how Maple can be used to encrypt and decrypt messages using shift and affine ciphers. It also shows how MATLAB can be used to encrypt and decrypt messages using shift and affine ciphers. Using findstr as in the preceding command instructs MATLAB to find the indices in which the array message contains a blank space, as indicated by the blank space enclosed by single quotes in the command.
