private static KeyStore getAndroidKeyStore() throws KeyStoreException {
		final KeyStore keystore = mAndroidKeystore.get();
		if (keystore == null) throw new KeyStoreException("Android keystore initialization error");
		return keystore;
	}
Utility for signing and verification with Android Keystore.

Created by Oasis on 2017/9/22.
engine/src/main/java/com/oasisfeng/island/util/Cryptography.java