Confusion about Encryption in iOS

Question

I'm a very newb programmer trying to write some iOS programs, and when I reached the part where I must encrypt my data, I ran into a misty and ill-documented wall. Apple apparently provides all the tools one needs to encrypt data but doesn't write about it anywhere. Currently I am experimenting with stuff found in https://github.com/AlanQuatermain/aqtoolkit, which apparently work. However, I read in http://robnapier.net/blog/aes-commoncrypto-564 that one should not use user selected passwords as encryption keys, but I have seen a few examples of people using the user's password directly with this library and others. Does this apply here, and should I run the user password through a small hurdle race before using it?

Answer 1

It is a good idea to use the hash of a password as a key for your crypto routines. One reason for that is that different algorithms may need keys of a different length and by selecting the appropriate hashing algorithm (e.g. SHA256 for AES256) you automatically get a key with the appropriate length.