What is Cryptography Cryptography, to most people, is concerned with keeping communications private. Indeed, the protection of sensitive communications has been the emphasis of cryptography throughout much of its history. As we will see, however, this is only one part of today s cryptography.
Encryption is the transformation of data into some unreadable form.
Its purpose is to ensure privacy by keeping the information hidden from anyone for whom it is not intended, even those who can see the encrypted data. Encryption and decryption require the use of some secret information, usually referred to as a key . Depending on the encryption mechanism used, the same key might be used for both encryption and decryption, while for other mechanisms, the keys used for encryption and decryption might be different. But today s cryptography is more than secret writing, more than encryption and decryption. Authentication is as fundamental a part of our lives as privacy.