Simple encrypt/decrypt is misleading

[gavin-black]

The simpler encrypt/decrypt functions are somewhat misleading. To actually use them you must have a padded derived key. It could be updated by default to produce some seemingly okay salt based the password. Right now a user must:

    NSData *salt = IMSCryptoUtilsPseudoRandomData(8);
    NSData *key = // Grabbed from wherever.
    key = IMSCryptoUtilsDeriveKey(key, kCCKeySizeAES256, salt);