TelephonyManager.getDeviceId() returns a constant value?
<p>I'm generating a key for obfuscate information. </p>

<p>That key must change between devices so for the generation I was using:</p>

<ul>
<li><code>Secure.getString(getContentResolver(), Secure.ANDROID_ID)</code></li>
<li><code>TelephonyManager.getSimSerialNumber()</code></li>
<li><code>TelephonyManager.getDeviceId()</code></li>
<li>A random persistent String generated if all of the options above are <code>null</code></li>
</ul>

<p>But testing I realised that since <strong>TelephonyManager.getSimSerialNumber()</strong> changes with the SIM in the device (and in airplane mode always return null) the key also changes and the obfuscated data cant be recovered.</p>

<p>My question is: Does <strong>TelephonyManager.getDeviceId()</strong> return always the same value (null or a value but always the same result)?</p>

<p>Note: I tested and it returns a valid value for me even in "Airplane mode"</p>
