Java Cryptography

Cryptography

Cryptography is the science of secret writing. It’s a branch of mathematics, part of cryptology . Cryptology has one other child, cryptanalysis , which is the science of breaking (analyzing) cryptography.

The main security concerns of applications are addressed by cryptography. First, applications need assurance that users are who they say they are. Proving identity is called authentication . In the physical world, a driver’s license is a kind of authentication. When you use a computer, you usually use a name and password to authenticate yourself. Cryptography provides stronger methods of authentication, called signatures and certificates. I’ll talk about these in Chapter 6.

Computer applications need to protect their data from unauthorized access. You don’t want people snooping on your data (you want confidentiality ), and you don’t want someone changing data without your knowledge (you want to be assured of your data’s integrity). Data stored on a disk, for example, may be vulnerable to being viewed or stolen. Data transmitted across a network is subject to all sorts of nefarious attacks. Again, cryptography provides solutions; I’ll discuss them in detail in Chapter 6 and Chapter 7.

So what can you do with cryptography? Plenty. Here are just a few examples:

Secure network communications

Cryptography can protect your data from thieves and impostors. Most web browsers now support SSL, a cryptographic protocol that encrypts information before it is transmitted over the Internet. ...