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jDLMS is a library implementing the DLMS/COSEM (IEC 62056) communication standard.

There is a newer version: 1.8.0

/*
 * Copyright 2012-16 Fraunhofer ISE
 *
 * This file is part of jDLMS.
 * For more information visit http://www.openmuc.org
 *
 * jDLMS is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * jDLMS is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with jDLMS.  If not, see .
 *
 */
package org.openmuc.jdlms.internal.security;

import java.io.IOException;
import java.nio.ByteBuffer;

import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.engines.AESFastEngine;
import org.bouncycastle.crypto.macs.GMac;
import org.bouncycastle.crypto.modes.GCMBlockCipher;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;

public class HlsProcessorGmac implements HlsSecretProcessor {

    private static final int SECURITY_CONTROL_BYTE_AUTHENTICATION = 0x10;

    @Override
    public byte[] process(byte[] challenge, byte[] authenticationKey, byte[] encryptionKey, byte[] systemTitle,
            int frameCounter) throws IOException, UnsupportedOperationException {

        byte[] sc = new byte[] { SECURITY_CONTROL_BYTE_AUTHENTICATION };
        byte[] frameCounterBytes = ByteBuffer.allocate(4).putInt(frameCounter).array();
        byte[] iv = ByteBuffer.allocate(systemTitle.length + frameCounterBytes.length)
                .put(systemTitle)
                .put(frameCounterBytes)
                .array();

        CipherParameters cipherParameters = new KeyParameter(encryptionKey);
        ParametersWithIV parameterWithIV = new ParametersWithIV(cipherParameters, iv);

        GMac mac = new GMac(new GCMBlockCipher(new AESFastEngine()), 96);

        mac.init(parameterWithIV);

        byte[] input = ByteBuffer.allocate(sc.length + authenticationKey.length + challenge.length)
                .put(sc)
                .put(authenticationKey)
                .put(challenge)
                .array();
        mac.update(input, 0, input.length);
        final byte[] generatedMac = new byte[mac.getMacSize()];
        mac.doFinal(generatedMac, 0);

        return ByteBuffer.allocate(sc.length + frameCounterBytes.length + generatedMac.length)
                .put(sc)
                .put(frameCounterBytes)
                .put(generatedMac)
                .array();
    }

}