rsa工具类

public class RSAUtil {
	/**
	 * 填充方式
	 */
	public static enum PADDING { NoPadding, PKCS1Padding };    
	/**
	 * 算法
	 */
	public static final String KEY_ALGORITHM = "RSA";
	/**
	 * 算法/工作模式
	 */
	public final static String CHIPER_ALGORITHM = "RSA/ECB/";
	/**
	 * 密钥长度
	 */
	public static final int KEY_SIZE = 1024;

	/**
	 * 65537 or 0x010001
	 */
	public static final byte[] PUBLIC_EXPONENT = { 1, 0, 1 };

	/**
	 * 生成密钥对
	 * 
	 * @return KeyPair
	 */
	public static KeyPair generateKeyPair() {
		try {
			KeyPairGenerator keyPairGen = KeyPairGenerator
					.getInstance(KEY_ALGORITHM);
			keyPairGen.initialize(KEY_SIZE, new SecureRandom());
			KeyPair keyPair = keyPairGen.genKeyPair();
			return keyPair;
		} catch (Exception e) {
			throw new RuntimeException("Error when init key pair, errmsg: "
					+ e.getMessage(), e);
		}
	}

	/**
	 * 生成公钥
	 * 
	 * @param modulus
	 * @param publicEXPonent
	 * @return RSAPublicKey
	 */
	private static RSAPublicKey generateRSAPublicKey(byte[] modulus,
			byte[] publicExponent) {
		try {
			RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(
					1, modulus), new BigInteger(1, publicExponent));
			KeyFactory keyFac = KeyFactory.getInstance(KEY_ALGORITHM);
			return (RSAPublicKey) keyFac.generatePublic(pubKeySpec);
		} catch (Exception e) {
			throw new RuntimeException(
					"Error when generate rsaPubblicKey, errmsg: "
							+ e.getMessage(), e);
		}

	}

	/**
	 * 生成私钥
	 * 
	 * @param modulus
	 * @param privateExponent
	 * @return RSAPrivateKey
	 */
	private static RSAPrivateKey generateRSAPrivateKey(byte[] modulus,
			byte[] privateExponent) {
		try {
			KeyFactory keyFac = KeyFactory.getInstance(KEY_ALGORITHM);
			RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(
					new BigInteger(1, modulus), new BigInteger(1,
							privateExponent));
			return (RSAPrivateKey) keyFac.generatePrivate(priKeySpec);
		} catch (Exception e) {
			throw new RuntimeException(
					"Error when generate rsaPrivateKey, errmsg: "
							+ e.getMessage(), e);
		}
	}

	/**
	 * 加密
	 * 
	 * @param key
	 *            加密的密钥
	 * @param data
	 *            待加密的明文数据
	 * @return 加密后的数据
	 */
	private static byte[] encrypt(Key key, byte[] data,PADDING padding) {
		try {
			Cipher cipher = Cipher.getInstance(CHIPER_ALGORITHM+(padding==null?PADDING.NoPadding:padding));
			cipher.init(Cipher.ENCRYPT_MODE, key);
			return cipher.doFinal(data);
		} catch (Exception e) {
			throw new RuntimeException("Error when encrypt data, errmsg: "
					+ e.getMessage(), e);
		}
	}

	/**
	 * 公钥加密
	 * 
	 * @param publicKey
	 * @param data
	 * @return
	 */
	public static byte[] encryptByPublicKey(byte[] publicKey, byte[] data,PADDING padding) {
		// 得到公钥
		RSAPublicKey key = generateRSAPublicKey(publicKey, PUBLIC_EXPONENT);
		// 加密
		return encrypt(key, data,padding);
	}

	/**
	 * 私钥加密
	 * 
	 * @param publicKey
	 * @param privateKey
	 * @param data
	 * @return
	 */
	public static byte[] encryptByPrivateKey(byte[] publicKey,
			byte[] privateKey, byte[] data,PADDING padding) {
		// 得到私钥
		RSAPrivateKey key = generateRSAPrivateKey(publicKey, privateKey);
		// 加密
		return encrypt(key, data,padding);
	}

	/**
	 * 解密
	 * 
	 * @param key
	 *            解密的密钥
	 * @param data
	 *            已经加密的数据
	 * @return 解密后的明文
	 */
	private static byte[] decrypt(Key key, byte[] data,PADDING padding) {
		try {
			Cipher cipher = Cipher.getInstance(CHIPER_ALGORITHM+(padding==null?PADDING.NoPadding:padding));
			cipher.init(Cipher.DECRYPT_MODE, key);
			return cipher.doFinal(data);
		} catch (Exception e) {
			throw new RuntimeException("Error when decrypt data, errmsg: "
					+ e.getMessage(), e);
		}
	}

	/**
	 * 公钥解密
	 * 
	 * @param publicKey
	 * @param data
	 * @ret公钥urn
	 */
	public static byte[] decryptByPublicKey(byte[] publicKey, byte[] data,PADDING padding) {
		// 得到公钥
		RSAPublicKey key = generateRSAPublicKey(publicKey, PUBLIC_EXPONENT);
		// 解密
		return decrypt(key, data,padding);
	}

	/**
	 * 私钥解密
	 * 
	 * @param publicKey
	 * @param privateKey
	 * @param data
	 * @return 
	 */
	public static byte[] decryptByPrivateKey(byte[] publicKey,
			byte[] privateKey, byte[] data,PADDING padding) {
		// 得到私钥
		RSAPrivateKey key = generateRSAPrivateKey(publicKey, privateKey);
		// 解密
		return decrypt(key, data,padding);
	}