exity comes in the additions of integer values. What if, for example, instead of "11" being used to signify the letter "A", the string "AX779423885PQM1299782242316a820203$$$$412" was used? There would be created ciphers of amazing complexity. It cannot be done manually but it can be done rapidly by computers, using cryptographic engines. This is accomplished by something called a "decryption engine" running a "decryption key" that receives messages from an "encryption engine using an "encryption key" (Kideki & Hartmanis, 1998; Schneier, 1995)
Concerning the "keys" there are two broad kinds of keys that control encryption and decryption. These keys are known as "public" and "private." In the example above, for the cipher for the letter "A" -- "AX779423885PQM1299782242316a 820203$$$$412" is only going to be meaningful if the person who receives the message knows that that string of integers means "A".
Anyone can create an encryption system, and all of them are designed to allow information to be safely transmitted in a digital format between computers. Reliability means that the cryptosystem, when used as its designer intended it to be used, will always reveal exactly the information hidden when it is needed (in other words, that the ciphertext will always be recoverable and the recovered data will be the same as to the original plaintext)(Crandall & Pomerance, 2001).
Security means that the cryptosystem will in fact keep the information hidden from all but those persons intended to see it despite the attempts of others to crack the system. The most important aspect of a system is that it should be easy to use. For instance, a very popular encryption program is a 256 bit key, an example of which is "1923A24C98D98F83E24 234CF8492C384E9AD19A128B3910F3904C324E920DA31." This is hard to remember, and hard to type manually. Because of this, people might be tempted to copy it and store it on a disc, which then destroys the v...