title: Touch ID for KeyChain no PIN fallback
body: <p>I am working to integrate touch ID for my App for user login. since I am going to store the username and password to be used in the future by touch, I found that localAuthenticate will not work for me and i have to use the new ACL to access the keychain.</p>
  
  <p>I got all the code to read/write to the keychain with ACL fine. but I see only right now one option "kSecAccessControlUserPresence" for SecAccessControlCreateFlags in SecAccessControlCreateWithFlags(...). this is allowing the user per apple documentation to fallback to the PIN code if they do not want to use touch ID. is there anyway to only allow the access to those keys with touch ID, and if it failed then the user has to enter there credentials manually?</p>
  
  <p>I have other alternatives but I am trying to avoid them:</p>
  
  <ul>
  <li><p>Option A: Use LocalAuthenticate and I will do the encryption for my credential in userdeafults but i have to figure out where to store the key? any ideas?</p></li>
  <li><p>Option B: keep using ACL and key Chain but I have to figure out if there is away if the user used PIN code or touch id. if they used touch id then I will go ahead an use the info i got from key chain to log in, if they used pin and I will ask them again with LocalAuthenticate. if they canceled it then i will not log in, if they verified with touch id then i will use the credential from keychain to login.</p></li>
  </ul>
  
  <p>UPDATE: Just in case someone asked why i do not want the PIN, Our lawyers did not accept the concept of a 4 digit pin code as way to access they key chain where we store the passwords. </p>