The DevX.com site has posted an introductory guide to using cryptography in PHP, showing how to use the various packages the language has to offer.

Cryptography is just one piece of the security puzzle, along with SSL/TLS, certificates, digital signatures, and so on. This article explains how to use PHP to implement the most common cryptographic algorithms. In addition to describing PHP's default encryption functions, you'll see how to use a wide variety of cryptographic libraries and packages.

They start with a look at some of the built-in functions like md5, sh1 and crypt as well as a table detailing the different encryption methods (like mcrypt, mhash or crypt_blowfish). They follow this up with examples of some of them including a method for making secret keys with the Crypt_DiffieHellman PEAR Package.

WebReference.com has posted part two in their series looking at security techniques in PHP. This time they focus on the use of a few things - the PECL filter, the PEAR Auth module and mcrypt.

For each of the three topics covered, they include a few code examples on their use - an HTML form with the filter extension, user authentication with the PEAR Auth, and encrypting data to be used in a more secure cookie.

The article is excerpted from PHP 5 Advanced: Visual QuickPro Guide by Larry Ullman.