Cryptography provides a set of techniques for encoding data and messages such that the data and messages can be stored and transmitted securely. This section introduces the basic terminology of cryptography and explains some of the common methods used.
Cryptography can be used to achieve secure communications, even when the transmission media (for example, the Internet) is untrustworthy. You can also use cryptography to encrypt your sensitive files, so that an intruder cannot understand them.
Cryptography can be used to ensure data integrity as well as maintain secrecy.
Using cryptography, it becomes possible to verify the origin of data and messages. This is done using digital signatures, which are explained a little later in this chapter.
When using cryptographic methods, the only part that must remain secret is the cryptographic keys. The algorithms, the key sizes, and file formats can be made public without compromising security.