RSA加密

RSA是一种不对称的加密方式，下面是RSA的使用代码：

import org.apache.commons.codec.binary.Base64;
import javax.crypto.Cipher;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
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;

/**
 * RSA加密工具类
 * @author songyan
 *
 */
public class RSADemo {
    
    /**
     * 生成一对密钥并将其存放在Map中
     * @throws NoSuchAlgorithmException
     */
    public static Map<String, String>  genKeyPair() throws NoSuchAlgorithmException {  
         Map<String, String> keyMap = new HashMap<String, String>();
        // KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象  
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");  
        // 初始化密钥对生成器，密钥大小为96-1024位  
        keyPairGen.initialize(1024,new SecureRandom());  
        // 生成一个密钥对，保存在keyPair中  
        KeyPair keyPair = keyPairGen.generateKeyPair();  
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();   // 得到私钥  
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();  // 得到公钥  
        String publicKeyString = new String(Base64.encodeBase64(publicKey.getEncoded()));  
        // 得到私钥字符串  
        String privateKeyString = new String(Base64.encodeBase64((privateKey.getEncoded())));  
        // 将公钥和私钥保存到Map
        keyMap.put("publicKey",publicKeyString);  //0表示公钥
        keyMap.put("privateKey",privateKeyString);  //1表示私钥
        
        return keyMap;
    }  
    
    /**
     * 
     * @param str 要加密的字符串
     * @param publicKey 公钥
     * @return 对str使用publicKey加密后的密文
     * @throws Exception
     */
    public static String encrypt( String str, String publicKey ) throws Exception{
        //base64编码的公钥
        byte[] decoded = Base64.decodeBase64(publicKey);
        RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(decoded));
        //RSA加密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);
        String outStr = Base64.encodeBase64String(cipher.doFinal(str.getBytes("UTF-8")));
        return outStr;
    }
    
    /**
     * 
     * @param publicKey 公钥加密后的密文
     * @param publicKey 私钥
     * @return 使用publicKey对str加密后的明文
     * @throws Exception
     */
    public static String decrypt(String str, String privateKey) throws Exception{
        //64位解码加密后的字符串
        byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));
        //base64编码的私钥
        byte[] decoded = Base64.decodeBase64(privateKey);  
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(decoded));  
        //RSA解密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        String outStr = new String(cipher.doFinal(inputByte));
        return outStr;
    }
    
    public static void main(String[] args) throws Exception {
         //生成公钥和私钥
         Map keyMap = genKeyPair();
         String publicKey = (String)keyMap.get("publicKey");
         String privateKey= (String)keyMap.get("privateKey");
    
        //加密字符串
        String target = "123456";
        
        //输出公钥私钥
        System.out.println("公钥:" + publicKey );
        System.out.println("私钥:" + privateKey);
        
        //公钥加密
        String messageEn = encrypt(target,publicKey);
        System.out.println("要加密的字符串为:" + target);
        System.out.println("加密后的字符串为:" + messageEn);
        
        //私钥解密
        String messageDe = decrypt(messageEn,privateKey);
        System.out.println("解密后的字符串:" + messageDe);
    }

}