CMAC 算法java代码

以下是一个示例的 CMAC 算法的 Java 代码：

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.Mac;

public class CMAC {
    private static final int BLOCK_SIZE = 16;
    private static final byte[] ZERO_PADDING = new byte[BLOCK_SIZE];

    public static byte[] generateCMAC(byte[] key, byte[] message) throws NoSuchAlgorithmException {
        byte[] subKey1 = generateSubKey(key, 0x00);
        byte[] subKey2 = generateSubKey(key, 0x01);

        byte[] paddedMessage = applyPadding(message);
        byte[] cmac = calculateCMAC(subKey1, subKey2, paddedMessage);

        return cmac;
    }

    private static byte[] generateSubKey(byte[] key, int constant) throws NoSuchAlgorithmException {
        SecretKeySpec keySpec = new SecretKeySpec(key, "AES");

        Mac mac = Mac.getInstance("HmacSHA256");
        mac.init(keySpec);

        byte[] constantBytes = new byte[BLOCK_SIZE];
        constantBytes[0] = (byte) (constant << 1);

        byte[] subKey = mac.doFinal(constantBytes);

        return subKey;
    }

    private static byte[] applyPadding(byte[] message) {
        int paddingLength = BLOCK_SIZE - (message.length % BLOCK_SIZE);
        byte[] paddedMessage = new byte[message.length + paddingLength];
        System.arraycopy(message, 0, paddedMessage, 0, message.length);
        System.arraycopy(ZERO_PADDING, 0, paddedMessage, message.length, paddingLength);

        return paddedMessage;
    }

    private static byte[] calculateCMAC(byte[] subKey1, byte[] subKey2, byte[] message) throws NoSuchAlgorithmException {
        MessageDigest md = MessageDigest.getInstance("SHA-256");

        byte[] x = new byte[BLOCK_SIZE];
        byte[] y = new byte[BLOCK_SIZE];

        int numBlocks = message.length / BLOCK_SIZE;
        for (int i = 0; i < numBlocks; i++) {
            for (int j = 0; j < BLOCK_SIZE; j++) {
                x[j] = (byte) (message[i * BLOCK_SIZE + j] ^ y[j]);
            }

            md.update(x);
            y = md.digest();
        }

        byte[] lastBlock = new byte[BLOCK_SIZE];