used was the one called the Caesar cipher, used by Julius Caesar to send messages to his generals to protect against the possibility of interception. It consisted of switching each alphabetic letter to the letter that was three letters down in the alphabet. For example, "Caesar" would become "Fdhvdu". This algorithm was later improved and renamed ROT13. This algorithm allowed the letters to be shifted to any letter between 1 and 25 in the alphabet, and the number of letters shifted was the key. A simple step away from ROT13 is Mono-alphabetic substitution. In this algorithm, each letter corresponds to another letter but in no particular order. For example a = m, s = p, and z = d, etc for all 26 letters. This made the algorithm harder to break, but also made for large keys that couldn't be memorized because they consisted of 26 pairs of letters.
             Blaise de Vigenere developed a poly-alphabetic substitution known as the Vigenere cipher. The algorithm encrypts messages several letters at a time instead of letter by letter. For example fh = lm, yz = ef. To simplify making the key that would be required for this for such an algorithm, a table is used in conjunction with the key. The table would be fairly large, but the key would be small enough to be memorized and the table would be useless without the key. This cipher wasn't totally safe, but no sure method of breaking was developed until the 20th century.
             Sir Francis Bacon's biliteral cipher employed an arrangement of the alphabetic letters 'a' and 'b' in five-letter combinations each representing a letter of the alphabet. This illustrates the principle that a code employing only two different signs can be used to transmit data.
             Currently, corporations and individuals use encryption to increase the security of their information. Soon, nearly all electronic communications will be cryptographically protected.
             In...