Java Cryptography

Secure Systems

Computer applications enable people to do work. Applications are parts of a larger system (a business, usually) that also involves people, fax machines, white boards, credit cards, paper forms, and anything else that makes the whole system run. Secure systems make it hard for people to do things they are not supposed to do. For example, a bank is designed as a secure system. You shouldn’t be able to withdraw money from someone else’s account, whether you try at the teller window, or by using the bank machine, or by telephone. Of course, you could bribe the teller or disassemble the bank machine, but these things are usually not worth the cost.

Secure systems are designed so that the cost of breaking any component of the system outweighs the rewards. Cost is usually measured in money, time, and risk, both legal and personal. The benefits of breaking systems are generally control, money, or information that can be sold for money. The security of the system should be proportional to the resources it protects; it should be a lot harder to break into a brokerage than a magazine subscription list, for example.

The term “secure systems” is a little misleading; it implies that systems are either secure or insecure. In truth, there is no absolute security. Every system can be broken, given enough time and money. Let me say that again, every system can be broken. There are more secure and less secure systems, but no totally secure systems. When people talk about secure systems, ...