SDK for Android:How facebook check the Hash key?

Question

When we want to use Facebook SDK for Android as our SSO solution, we need to put our Android application signature into our Facebook application settings (Step 5 of Facebook sdk for android).

And that signature should be generated by running the keytool that comes with the Android SDK.

I am curious how facebook verify this signature?

Answer 1

After more than one year, I think I'd better answer my question.

Android's app can get other app's signature by:

public String WriteSignature(String packageName)
{     
   PackageManager pm = this.getPackageManager();
   String sig = ""; 
   PackageInfo pi = null;
   try {
       pi = pm.getPackageInfo(packageName, PackageManager.GET_SIGNATURES);
   } catch (NameNotFoundException e1) {
       e1.printStackTrace();
   }

   try {
       for (Signature signature : pi.signatures) {
           MessageDigest md = MessageDigest.getInstance("SHA");
           md.update(signature.toByteArray());
           sig = Base64.encodeToString(md.digest(), Base64.DEFAULT);
           Log.d(ACTIVITY_TAG, sig);
       }
   } catch (NoSuchAlgorithmException e) {
       e.printStackTrace();
   }

   return sig;
}