title: How do I use Apple Keychain?
body: <p>I am using trying to use <a href="http://github.com/ldandersen/scifihifi-iphone/tree/master/security" rel="noreferrer">scifihifi-iphone (from Github)</a> to store and retrieve usernames and passwords. However, when I add the class <code>SFHFKeychainUtils</code> I get the following errors:</p>
  
  <pre><code>  "_kSecAttrAccount", referenced from:
        _kSecAttrAccount$non_lazy_ptr in SFHFKeychainUtils.o
    "_SecItemDelete", referenced from:
        +[SFHFKeychainUtils deleteItemForUsername:andServiceName:error:] in SFHFKeychainUtils.o
    "_kSecReturnAttributes", referenced from:
        _kSecReturnAttributes$non_lazy_ptr in SFHFKeychainUtils.o
    "_kSecClass", referenced from:
        _kSecClass$non_lazy_ptr in SFHFKeychainUtils.o
    "_kSecClassGenericPassword", referenced from:
        _kSecClassGenericPassword$non_lazy_ptr in SFHFKeychainUtils.o
    "_SecItemAdd", referenced from:
        +[SFHFKeychainUtils storeUsername:andPassword:forServiceName:updateExisting:error:] in SFHFKeychainUtils.o
    "_kSecAttrLabel", referenced from:
        _kSecAttrLabel$non_lazy_ptr in SFHFKeychainUtils.o
    "_SecItemUpdate", referenced from:
        +[SFHFKeychainUtils storeUsername:andPassword:forServiceName:updateExisting:error:] in SFHFKeychainUtils.o
    "_kSecAttrService", referenced from:
        _kSecAttrService$non_lazy_ptr in SFHFKeychainUtils.o
    "_kSecReturnData", referenced from:
        _kSecReturnData$non_lazy_ptr in SFHFKeychainUtils.o
    "_SecItemCopyMatching", referenced from:
        +[SFHFKeychainUtils getPasswordForUsername:andServiceName:error:] in SFHFKeychainUtils.o
        +[SFHFKeychainUtils getPasswordForUsername:andServiceName:error:] in SFHFKeychainUtils.o
    "_kSecValueData", referenced from:
        _kSecValueData$non_lazy_ptr in SFHFKeychainUtils.o
  ld: symbol(s) not found
  collect2: ld returned 1 exit status
  </code></pre>
  
  <p>What am I leaving out? When I click the errors, it doesn't take me to any place in the code.</p>