public static Mode getNormalized(String modeString) {
            modeString = modeString.toUpperCase(Locale.US);
            // We use GCM-SIV as the mode string, but - isn't a valid identifier character, so
            // we need to ensure GCM-SIV is recognized and GCM_SIV isn't.
            if (modeString.equals("GCM-SIV")) {
                return GCM_SIV;
            } else if (modeString.equals("GCM_SIV")) {
                throw new IllegalArgumentException("Invalid mode");
            } else {
                return Mode.valueOf(modeString);
            }
        }
Modes that a block cipher may support.
common/src/main/java/org/conscrypt/OpenSSLCipher.java