Here’s a great wrapper that really simplifies working with KeyChain in iOS //log.scifihifi.com/post/55837387/simple-iphone-keychain-code. The code is on GitHub as well //github.com/ldandersen/scifihifi-iphone/tree/master/security/.

Apple’s official documentation is here, and there is also a sample project, but it’s not a good example for getting up and running quickly. The version of the project (last updated 10/2009) doesn’t even run on the simulator.