Randomly generates an encryption key for devices with API level lower than 18.

setSecretKey.java

// Devices with API level lower than 18 must setup an encryption key.
if (Build.VERSION.SDK_INT < 18 && AuthenticationSettings.INSTANCE.getSecretKeyData() == null) {
        AuthenticationSettings.INSTANCE.setSecretKey(generateSecretKey());
}

/**
 * Randomly generates an encryption key for devices with API level lower than 18.
 * @return The encryption key in a 32 byte long array.
 */
protected byte[] generateSecretKey() {
    byte[] key = new byte[32];
    new SecureRandom().nextBytes(key);
    return key;
}