title: What is 'android.security.MessageDigest''?
body: <p>One of several thousand customers reported an error in one of my apps. The error is:</p>
  
  <pre><code>java.lang.NoClassDefFoundError - android.security.MessageDigest
  </code></pre>
  
  <p>I don't use that class/method in my apps. The Google Mapkey must be ok because there are thousands running the same app with the same version happily. Here's the stacktrace:</p>
  
  <pre><code>java.lang.NoClassDefFoundError: android.security.MessageDigest
  at com.google.android.maps.KeyHelper.getSignatureFingerprint(KeyHelper.java:60)
  at com.google.android.maps.MapActivity.createMap(MapActivity.java:552)
  at com.google.android.maps.MapActivity.onCreate(MapActivity.java:422)
  at xx.yyy.zzzz.MyMapActivity.onCreate(MyMapActivity.java:41)
  at xx.yyy.zzzz.TheMap.onCreate(TheMap.java:89)
  at android.app.Activity.performCreate(Activity.java:4465)
  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
  at android.app.ActivityThread.access$600(ActivityThread.java:123)
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
  at android.os.Handler.dispatchMessage(Handler.java:99)
  at android.os.Looper.loop(Looper.java:137)
  at android.app.ActivityThread.main(ActivityThread.java:4424)
  at java.lang.reflect.Method.invokeNative(Native Method)
  at java.lang.reflect.Method.invoke(Method.java:511)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
  at dalvik.system.NativeStart.main(Native Method)
  </code></pre>
  
  <p>What is this?</p>
  
  <p>Thanks in advance.</p>