I need to encrypt and decrypt NSStrings. It doesn't have to be secure (at all!) just unreadable to an average user. Something as simple as a shift cipher would work alright, but I would like an algorithm slightly less obvious to the user.
Is there something built in to the iOS sdk that does this already? Maybe RSA encryption? Or a simple to code algorithm that wouldn't look like a one to one character exchange? Thank you!
How about Base64.
It's completely non-secure, and although unreadable it will be a fairly obvious encoding scheme for anyone remotely knowledgeable in IT.
Implementation details : How do I do base64 encoding on iphone-sdk?
What about ROT13? It was already used in ancient Rome, fun to use, not save.
Or use string encoding as used for URLs in web technologies.
You could use a substitution cypher. Just prepare a 255 byte array with indexes from 1 to 255, scramble the array and replace each byte with the corresponding index value. Another easy cypher employs a key of length N, consisting of positive and negative offsets. Each byte of the nsstring gets shifted - the first by the value of the first offset, the second by the second and the k-th by the value of the (k mod N)-the. It is much harder to spot for the average, unmotivated user, and almost as easy to implement as a single shift cypher.
