Over the years Apple has slowly but surely filled in some pretty conspicuous gaps in their application platform for iOS developers. They didn’t even support working with JSON data until iOS 5 introduced NSJSONSerialization! Another small, but important, gap that was filled in by iOS 7 is proper support for encoding and decoding data in Base64; such as base64EncodedStringWithOptions: and initWithBase64EncodedString:options:.
NSHipster has a good, quick overview of what Base64 is all about with an example here.
StackOverflow shows how to both encode and decode in Base64 here.
Learn more about Base64 encoding on the Wikipedia page here.
Thanks Apple! It’s about time…