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Code: Select all

byte[] mac;
byte[] icv = new byte[8];
Cipher desedeCBCCipher = Cipher.getInstance("DESede/CBC/NoPadding");
Cipher desCipher = Cipher.getInstance("DES/CBC/NoPadding");

IvParameterSpec ivSpec = new IvParameterSpec(icv);

if (data.length % 8 != 0)
    throw new Exception("data block size must be multiple of 8");

int blocks = data.length / 8;

for (int i = 0; i < blocks - 1; i++) {
    desCipher.init(Cipher.ENCRYPT_MODE, singledesCMAC, ivSpec);
    byte[] block = desCipher.doFinal(data, i * 8, 8);
    ivSpec = new IvParameterSpec(block);
}

int offset = (blocks - 1) * 8;

desedeCBCCipher.init(Cipher.ENCRYPT_MODE, sessionCMAC, ivSpec);
mac = desedeCBCCipher.doFinal(data, offset, 8);

ivSpec = new IvParameterSpec(new byte[8]);
desCipher.init(Cipher.ENCRYPT_MODE, singledesCMAC, ivSpec);
icv = desCipher.doFinal(data);

Code: Select all

private SecretKey getSecretKey(byte[] keyData) throws GeneralSecurityException {
    if (keyData.length == 16) {
        byte[] temp = (byte[]) keyData.clone();
        keyData = new byte[24];
        System.arraycopy(temp, 0, keyData, 0, temp.length);
        System.arraycopy(temp, 0, keyData, 16, 8);
    }

    DESedeKeySpec keySpec = new DESedeKeySpec(keyData);
    SecretKeyFactory secretKeyFactory = SecretKeyFactory.getInstance("DESede");
    SecretKey key = secretKeyFactory.generateSecret(keySpec);

    return key;
}

private Key deriveKey(byte[] keyData, byte[] data) throws GeneralSecurityException {
    Key key = getSecretKey(keyData);
    IvParameterSpec dps = new IvParameterSpec(DEFAULT_ICV);
    desedeCBCCipher.init(Cipher.ENCRYPT_MODE, key, dps);

    byte[] result = desedeCBCCipher.doFinal(data);
    adjustParity(result);

    return getSecretKey(result);
}


/**
 * Adjust a DES key to odd parity
 * 
 * @param key
 *            to be adjusted
 */
private static void adjustParity(byte[] key) {
    for (int i = 0; i < key.length; i++) {
        int akku = (key[i] & 0xFF) | 1;

        for (int c = 7; c > 0; c--) {
            akku = (akku & 1) ^ (akku >> 1);
        }
        key[i] = (byte) ((key[i] & 0xFE) | akku);
    }
}

Code: Select all

 /**
     * Calculate the DES CBC MAC using the standard cipher algorithms
     * 
     * @param key
     *            Key used for MAC calculation
     * @param data
     *            Data to calculate the MAC for
     * @param iv
     *            ICV
     * 
     * @returns CBC MAC
     */
    public byte[] cbcMac(byte[] data) throws AuthenticationException {

        byte[] temp;
        try {
            Cipher cbcDES = Cipher.getInstance("DESede/CBC/NoPadding");
            IvParameterSpec params = new IvParameterSpec(DEFAULT_ICV);
            cbcDES.init(Cipher.ENCRYPT_MODE, sessionSENC, params);

            temp = cbcDES.doFinal(data);
        } catch (GeneralSecurityException e) {
            throw new AuthenticationException("Error performing CBC MAC", e);
        }

        byte[] signature = new byte[8];
        System.arraycopy(temp, temp.length - 8, signature, 0, signature.length);
        return signature;
    }