[Trans]java实现RSA加密 .

http://blog.csdn.net/wxyfighting/article/details/9075215

java实现RSA加密

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。

    通过java代码实现如下：

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
*  
* @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 http://www.5a520.cn http://www.feng123.com
     *  
     * @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>
     * 用私钥解密
     *  
     * @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;  

/** *//**
*  
* @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);  

    }  

}