java 实现DH加密解密

public static final String ALGORITHM = "DH";

    /**
     * 默认密钥字节数
     *
     * <pre>
     * DH
     * Default Keysize 1024
     * Keysize must be a multiple of 64, ranging from 512 to 1024 (inclusive).
     * </pre>
     */
    private static final int KEY_SIZE = 1024;

    /**
     * DH加密下需要一种对称加密算法对数据加密，这里我们使用DES，也可以使用其他对称加密算法。
     */
    public static final String SECRET_ALGORITHM = "DES";
    private static final String PUBLIC_KEY = "DHPublicKey";
    private static final String PRIVATE_KEY = "DHPrivateKey";

    /**
     * 初始化甲方密钥
     * @return
     * @throws Exception
     */
    public static Map<String, Object> initKey() throws Exception {
        KeyPairGenerator keyPairGenerator = KeyPairGenerator
                .getInstance(ALGORITHM);
        keyPairGenerator.initialize(KEY_SIZE);

        KeyPair keyPair = keyPairGenerator.generateKeyPair();

        // 甲方公钥
        DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();

        // 甲方私钥
        DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();

        Map<String, Object> keyMap = new HashMap<String, Object>(2);

        keyMap.put(PUBLIC_KEY, publicKey);
        keyMap.put(PRIVATE_KEY, privateKey);
        return keyMap;
    }

    /**
     * 初始化乙方密钥
     * @param key 甲方公钥
     * @return
     * @throws Exception
     */
    public static Map<String, Object> initKey(String key) throws Exception {
        // 解析甲方公钥
        byte[] keyBytes = decryptBASE64(key);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
        PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);

        // 由甲方公钥构建乙方密钥
        DHParameterSpec dhParamSpec = ((DHPublicKey) pubKey).getParams();

        KeyPairGenerator keyPairGenerator = KeyPairGenerator
                .getInstance(keyFactory.getAlgorithm());
        keyPairGenerator.initialize(dhParamSpec);

        KeyPair keyPair = keyPairGenerator.generateKeyPair();

        // 乙方公钥
        DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();

        // 乙方私钥
        DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();

        Map<String, Object> keyMap = new HashMap<String, Object>(2);

        keyMap.put(PUBLIC_KEY, publicKey);
        keyMap.put(PRIVATE_KEY, privateKey);

        return keyMap;
    }

    /**
     * 加密<br>
     * @param data  待加密数据
     * @param publicKey 甲方公钥
     * @param privateKey 乙方私钥
     * @return
     * @throws Exception
     */
    public static byte[] encrypt(byte[] data, String publicKey,
                                 String privateKey) throws Exception {
        // 生成本地密钥
        SecretKey secretKey = getSecretKey(publicKey, privateKey);
        // 数据加密
        Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, secretKey);
        return cipher.doFinal(data);
    }

    /**
     * 解密<br>
     * @param data 待解密数据
     * @param publicKey 乙方公钥
     * @param privateKey 乙方私钥
     * @return
     * @throws Exception
     */
    public static byte[] decrypt(byte[] data, String publicKey,
                                 String privateKey) throws Exception {
        // 生成本地密钥
        SecretKey secretKey = getSecretKey(publicKey, privateKey);
        // 数据解密
        Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, secretKey);
        return cipher.doFinal(data);
    }

    /**
     * 构建密钥
     * @param publicKey 公钥
     * @param privateKey 私钥
     * @return
     * @throws Exception
     */
    private static SecretKey getSecretKey(String publicKey, String privateKey)
            throws Exception {
        // 初始化公钥
        byte[] pubKeyBytes = decryptBASE64(publicKey);
        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(pubKeyBytes);
        PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);
        // 初始化私钥
        byte[] priKeyBytes = decryptBASE64(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(priKeyBytes);
        Key priKey = keyFactory.generatePrivate(pkcs8KeySpec);
        KeyAgreement keyAgree = KeyAgreement.getInstance(keyFactory
                .getAlgorithm());
        keyAgree.init(priKey);
        keyAgree.doPhase(pubKey, true);
        // 生成本地密钥
        SecretKey secretKey = keyAgree.generateSecret(SECRET_ALGORITHM);
        return secretKey;
    }

    /**
     * 取得私钥
     * @param keyMap
     * @return
     * @throws Exception
     */
    public static String getPrivateKey(Map<String, Object> keyMap)
            throws Exception {
        Key key = (Key) keyMap.get(PRIVATE_KEY);
        return encryptBASE64(key.getEncoded());
    }

    /**
     * 取得公钥
     * @param keyMap
     * @return
     * @throws Exception
     */
    public static String getPublicKey(Map<String, Object> keyMap)
            throws Exception {
        Key key = (Key) keyMap.get(PUBLIC_KEY);
        return encryptBASE64(key.getEncoded());
    }

    /**
     * BASE64解密
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] decryptBASE64(String key) throws Exception {
        return (new BASE64Decoder()).decodeBuffer(key);
    }

    /**
     * BASE64加密
     * @param key
     * @return
     * @throws Exception
     */
    public static String encryptBASE64(byte[] key) throws Exception {
        return (new BASE64Encoder()).encodeBuffer(key);
    }

    public static void main(String[] args) throws Exception {
        // 生成甲方密钥对儿
        Map<String, Object> aKeyMap = initKey();
        String aPublicKey = getPublicKey(aKeyMap);
        String aPrivateKey = getPrivateKey(aKeyMap);

        System.err.println("甲方公钥:\r" + aPublicKey);
        System.err.println("甲方私钥:\r" + aPrivateKey);

        // 由甲方公钥产生本地密钥对儿
        Map<String, Object> bKeyMap = initKey(aPublicKey);
        String bPublicKey = getPublicKey(bKeyMap);
        String bPrivateKey = getPrivateKey(bKeyMap);

        System.err.println("乙方公钥:\r" + bPublicKey);
        System.err.println("乙方私钥:\r" + bPrivateKey);

        String aInput = "abc ";
        System.err.println("原文: " + aInput);

        // 由甲方公钥，乙方私钥构建密文
        byte[] aCode = encrypt(aInput.getBytes(), aPublicKey,
                bPrivateKey);

        // 由乙方公钥，甲方私钥解密
        byte[] aDecode = decrypt(aCode, bPublicKey, aPrivateKey);
        String aOutput = (new String(aDecode));

        System.err.println("解密: " + aOutput);

        System.err.println(" ===============反过来加密解密================== ");
        String bInput = "def ";
        System.err.println("原文: " + bInput);

        // 由乙方公钥，甲方私钥构建密文
        byte[] bCode = encrypt(bInput.getBytes(), bPublicKey,
                aPrivateKey);

        // 由甲方公钥，乙方私钥解密
        byte[] bDecode = decrypt(bCode, aPublicKey, bPrivateKey);
        String bOutput = (new String(bDecode));

        System.err.println("解密: " + bOutput);

    }