Cryptography
Cryptography refers to the hiding of information, both in practice and in study. In modern times, this practice involves elements of mathematics, electrical engineering and computer science. Many practical applications in current society, such as electronic commerce, ATM cards and computer passwords, are protected through cryptographic algorithms. Every time someone uses his or her bank card, logs into a website or buys something from the Internet, that person is benefiting from cryptographics and may not even realise it.
The core of cryptography is based firmly in science. The entire process is approached scientifically in order to create the most secure system possible. Cryptographic algorithms take factors such as computational hardness assumptions into account, for example. Computational hardness assumptions are estimates of how difficult it is to break the enforced security.
In theory, some cryptographic systems are so secure that they are unbreakable. Technically, most any security can be broken, but in a theoretically unbreakable system, the security is so good that it is not feasible for someone to break it via any practical means. Users can rest easy with a theoretically unbreakable system in place protecting their data.
On the reverse side of this is cryptanalysis. This refers to the study of how to find a weakness in a cryptographic scheme and break it. Though it may not sound that way, this theory is actually as important to security as cryptographing itself. No form of computer security is 100 per cent secure, and the best way to find out where the weaknesses are is through cryptanalysis.