title: Confused about how Android Encryption works
body: <p>Okay, I am working on an application and I want to store a file on the user's SD Card, but I want the file encrypted. I've researched several sites that use the DES encryption to encrypt files and data, but I am confused about something. All the examples I'm seen use a line like this:</p>
  
  <pre><code>SecretKey key = KeyGenerator.getInstance("DES").generateKey();
  </code></pre>
  
  <p>The problem I am having is that I get my key to encrypt and obviously I need the same key to decrypt. But its seems like a paradox because if I store my key in a file or in a database, can't someone get the key and decrypt my file? Maybe I am missing something, but is there a way to generate a key using a supplied pass phrase? And why would someone not want to use a passkey if they must store the generated key somewhere else?</p>