In a modern society, exchange and storage of information in an efficient, reliable and secure manner is of fundamental importance. The communication is almost always in a digital form, i.e., the information is represented as a sequence of discrete symbols. Examples of digital communication systems are wire-based and wireless transmission lines, network connections, hard disks for computers, HDTV, CD and DVD players. Digital mobile communication is becoming increasingly important. For example, there are now more than 3 million mobile telephones in Norway.
Any communication is to some extent affected by noise.
In order to detect or correct the errors that occur, the information is represented as a sequence of code words in an error-correcting code. The reliability of a communication system depends on physical conditions, but also on the error-correcting code and the decoding algorithm being used. Coding theory deals with methods to construct and analyze error-correcting codes and to decode them in an efficient manner. The quality of digital communication, in particular mobile communication, is totally dependent on efficient error correction. Cryptology comprises the interrelated areas of cryptography and cryptanalysis.