public String getString(String key, String defValue) {
        String result;
        String value = mPreferences.getString(key, null);
        if (value != null) {
            try {
                result = mObfuscator.unobfuscate(value, key);
            } catch (ValidationException e) {
                // Unable to unobfuscate, data corrupt or tampered
                Log.w(TAG, "Validation error while reading preference: " + key);
                result = defValue;
            }
        } else {
            // Preference not found
            result = defValue;
        }
        return result;
    }
Constructor.

@param sp A SharedPreferences instance provided by the system.
@param o The Obfuscator to use when reading or writing data.
android/android_framework/base/src/main/java/com/google/android/vending/licensing/PreferenceObfuscator.java