Text Encryption

[Fontano]

We are going to be implementing some REST WebServices, and we want to encrypt a key field in that call. Right now the targeted encryption algorithm is DES 3.

I've seen some documentation, but not a lot.
Is there a good resource explaining what is natively available to the iPhone SDK with regards to doing encryption.

Or maybe even a simple example of encoding and decoding a string done in DES 3

Thanks