Java加密技术—非对称加密算法RSA

RSA 
    这种算法1978年就出现了，它是第一个既能用于数据加密也能用于数字签名的算法。它易于理解和操作，也很流行。算法的名字以发明者的名字命名：Ron Rivest, AdiShamir 和Leonard Adleman。 
    这种加密算法的特点主要是密钥的变化，上文我们看到DES只有一个密钥。相当于只有一把钥匙，如果这把钥匙丢了，数据也就不安全了。RSA同时有两把钥匙，公钥与私钥。同时支持数字签名。数字签名的意义在于，对传输过来的数据进行校验。确保数据在传输工程中不被修改

流程分析： 

1. 甲方构建密钥对儿，将公钥公布给乙方，将私钥保留。
2. 甲方使用私钥加密数据，然后用私钥对加密后的数据签名，发送给乙方签名以及加密后的数据；乙方使用公钥、签名来验证待解密数据是否有效，如果有效使用公钥对数据解密。
3. 乙方使用公钥加密数据，向甲方发送经过加密后的数据；甲方获得加密数据，通过私钥解密。按如上步骤给出序列图，如下： 
   
   1. 
   2. 
   3. 

 
package com.lee.encrypt; 


import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;

/**
 * RSA安全编码组件
 * 
 * @author lee
 * @version 1.0
 * @since 1.0
 */
public abstract class RSACoder extends Coder {
    public static final String KEY_ALGORITHM = "RSA";
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

    private static final String PUBLIC_KEY = "RSAPublicKey";
    private static final String PRIVATE_KEY = "RSAPrivateKey";

    /**
     * 用私钥对信息生成数字签名
     * 
     * @param data
     *            加密数据
     * @param privateKey
     *            私钥
     * 
     * @return
     * @throws Exception
     */
    public static String sign(byte[] data, String privateKey) throws Exception {
        // 解密由base64编码的私钥
        byte[] keyBytes = decryptBASE64(privateKey);

        // 构造PKCS8EncodedKeySpec对象
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);

        // KEY_ALGORITHM 指定的加密算法
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

        // 取私钥匙对象
        PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);

        // 用私钥对信息生成数字签名
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initSign(priKey);
        signature.update(data);

        return encryptBASE64(signature.sign());
    }

    /**
     * 校验数字签名
     * 
     * @param data
     *            加密数据
     * @param publicKey
     *            公钥
     * @param sign
     *            数字签名
     * 
     * @return 校验成功返回true 失败返回false
     * @throws Exception
     * 
     */
    public static boolean verify(byte[] data, String publicKey, String sign)
            throws Exception {

        // 解密由base64编码的公钥
        byte[] keyBytes = decryptBASE64(publicKey);

        // 构造X509EncodedKeySpec对象
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);

        // KEY_ALGORITHM 指定的加密算法
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

        // 取公钥匙对象
        PublicKey pubKey = keyFactory.generatePublic(keySpec);

        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initVerify(pubKey);
        signature.update(data);

        // 验证签名是否正常
        return signature.verify(decryptBASE64(sign));
    }

    /**
     * 解密<br>
     * 用私钥解密
     * 
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] decryptByPrivateKey(byte[] data, String key)
            throws Exception {
        // 对密钥解密
        byte[] keyBytes = decryptBASE64(key);

        // 取得私钥
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);

        // 对数据解密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, privateKey);

        return cipher.doFinal(data);
    }

    /**
     * 解密<br>
     * 用公钥解密
     * 
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] decryptByPublicKey(byte[] data, String key)
            throws Exception {
        // 对密钥解密
        byte[] keyBytes = decryptBASE64(key);

        // 取得公钥
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicKey = keyFactory.generatePublic(x509KeySpec);

        // 对数据解密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, publicKey);

        return cipher.doFinal(data);
    }

    /**
     * 加密<br>
     * 用公钥加密
     * 
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] encryptByPublicKey(byte[] data, String key)
            throws Exception {
        // 对公钥解密
        byte[] keyBytes = decryptBASE64(key);

        // 取得公钥
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicKey = keyFactory.generatePublic(x509KeySpec);

        // 对数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);

        return cipher.doFinal(data);
    }

    /**
     * 加密<br>
     * 用私钥加密
     * 
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] encryptByPrivateKey(byte[] data, String key)
            throws Exception {
        // 对密钥解密
        byte[] keyBytes = decryptBASE64(key);

        // 取得私钥
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);

        // 对数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);

        return cipher.doFinal(data);
    }

    /**
     * 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());
    }

    /**
     * 初始化密钥
     * 
     * @return
     * @throws Exception
     */
    public static Map<String, Object> initKey() throws Exception {
        KeyPairGenerator keyPairGen = KeyPairGenerator
                .getInstance(KEY_ALGORITHM);
        keyPairGen.initialize(1024);

        KeyPair keyPair = keyPairGen.generateKeyPair();

        // 公钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();

        // 私钥
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();

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

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

  再给出一个测试类：  

 
package com.lee.encrypt; 



import static org.junit.Assert.*;

import org.junit.Before;
import org.junit.Test;

import java.util.Map;

/**
 * 
 * @author lee
 * @version 1.0
 * @since 1.0
 */
public class RSACoderTest {
    private String publicKey;
    private String privateKey;

    @Before
    public void setUp() throws Exception {
        Map<String, Object> keyMap = RSACoder.initKey();

        publicKey = RSACoder.getPublicKey(keyMap);
        privateKey = RSACoder.getPrivateKey(keyMap);
        System.err.println("公钥: \n\r" + publicKey);
        System.err.println("私钥： \n\r" + privateKey);
    }

    @Test
    public void test() throws Exception {
        System.err.println("公钥加密——私钥解密");
        String inputStr = "abc";
        byte[] data = inputStr.getBytes();

        byte[] encodedData = RSACoder.encryptByPublicKey(data, publicKey);

        byte[] decodedData = RSACoder.decryptByPrivateKey(encodedData,
                privateKey);

        String outputStr = new String(decodedData);
        System.err.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);
        assertEquals(inputStr, outputStr);

    }

    @Test
    public void testSign() throws Exception {
        System.err.println("私钥加密——公钥解密");
        String inputStr = "sign";
        byte[] data = inputStr.getBytes();

        byte[] encodedData = RSACoder.encryptByPrivateKey(data, privateKey);

        byte[] decodedData = RSACoder
                .decryptByPublicKey(encodedData, publicKey);

        String outputStr = new String(decodedData);
        System.err.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);
        assertEquals(inputStr, outputStr);

        System.err.println("私钥签名——公钥验证签名");
        // 产生签名
        String sign = RSACoder.sign(encodedData, privateKey);
        System.err.println("签名:\r" + sign);

        // 验证签名
        boolean status = RSACoder.verify(encodedData, publicKey, sign);
        System.err.println("状态:\r" + status);
        assertTrue(status);

    }

}

 控制台输出为：

公钥: 

MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDGB06cz4zuzfeO7eW9/bQ7wddDQsbf6WABeS5X
WTxIgda62DqK0ceQX6vOW6btbLXtdJV+SocCV9IIqrCm2ZY98LYEQ2dSN8963k5yHFvk0BIyA3Ez
2ZBD0GbSUzgTDWWMuMrdzYKKzirP6zaXVvKTi+p9fNz4D/wwVPQMpOyo7wIDAQAB

私钥： 
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公钥加密——私钥解密
加密前: abc

解密后: abc
公钥: 

MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCWqz0Fc8hcXNpT+uotIdOoskHb69k1VmSpmRvr
BFz3orrA7GtVUYACjtgfUdfz7tWGD1bF5fTKYRQMZ0e3Aij3oBa990YPGlBzSk3zYkGZvSPqRAOM
fjOb4EjfXPkOUv2aijlSNs0SNvGmJ1s9g7Zdaq8eO+9gk20VNusYriGxzwIDAQAB

私钥： 
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私钥加密——公钥解密
加密前: sign

解密后: sign
私钥签名——公钥验证签名
签名:
CXyvfEb4+KLS0PDbjyPbXjVHMkNBCOrpEhc1M/ZA3tWJ4PR509/QLsrzTUy7eaynFdqMqqB6sp7M
OQr1EDjN4WsEW1nObJfRvSX3Hz7CVwlYNHFaLIVbOvOjUDOTenNhVuK03MgfD29WA23L/AOU6hCi
P08X5DJnIqF//sN6R/Q=

状态:
true