非对称加密算法RSA--转

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： 

通过java代码实现如下：Coder类见 Java加密技术（一） 

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 梁栋

 * @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： 

import static org.junit.Assert.*;



import org.junit.Before;

import org.junit.Test;



import java.util.Map;



/**

 * 

 * @author 梁栋

 * @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);



    }



}

 

原文地址：http://snowolf.iteye.com/blog/381767