To most people, cryptography is concerned with keeping communications private. However, this is only one part of today's cryptography. Its purpose is to ensure privacy by keeping information hidden from anyone for whom it is not intended, even those who have access to the encrypted data. Encryption and decryption generally require the use of some secret information, referred to as a key . Today's cryptography is more than encryption and decryption.
Authentication is as fundamentally a part of our lives as privacy.
Cryptography provides mechanisms for such procedures. The field of cryptography encompasses other uses as well. While modern cryptography is growing increasingly diverse, cryptography is fundamentally based on problems that are difficult to solve. A problem may be difficult because its solution requires some secret knowledge, such as decrypting an encrypted message or signing some digital document.