The scientific field of providing security for information through the reversible alteration of data is known as cryptography. Cryptography is an ancient science that dates back to the time of Julius Caesar, who utilized a noncomplex letter substitution cipher that even today carries his name. Today, cryptographic systems are more secure and more complex than they were in CaesarÂ’s time. Improved by digital computing, cryptographic systems contain an algorithm as well as one or several keys. A cipher, or cryptographic algorithm, is the means of altering data from a readable form (also known as plaintext) to a protected form (also known as ciphertext), and back to the readable form. Changing plaintext to ciphertext is known as encryption, whereas changing ciphertext to plaintext is known as decryption.

See Also: Cryptography or “Crypto”; Ciphertext; Encryption or Encipher; Plaintext.