title: encrypting/ decrypting strings to text
body: <p>I am creating an app that would allow people to share sensitive info with each other via the iphone sms app. I want to make use of the security framework that apple provides, using keys that the people sharing that data know before hand to encrypt and decrypt strings. I don't have much knowledge about the whole keychain system on iOS devices or security protocols in general so does anyone know any good resources for learning about this stuff?</p>