RSA基本的介绍

RSA（Rivest-Shamir-Adleman）算法是目前最常用的公钥加密算法。

　　（1）乙方生成两把密钥（公钥和私钥）。公钥是公开的，任何人都可以获得，私钥则是保密的。

　　（2）甲方获取乙方的公钥，然后用它对信息加密。

　　（3）乙方得到加密后的信息，用私钥解密。

java的基本实现

需要的依赖

<!-- https://mvnrepository.com/artifact/commons-codec/commons-codec -->
<dependency>
    <groupId>commons-codec</groupId>
    <artifactId>commons-codec</artifactId>
    <version>1.15</version>
</dependency>

java代码基本实现

package com.jianfreespace;

import org.apache.commons.codec.binary.Base64;
import javax.crypto.Cipher;
import java.security.*;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;


public class RSAUtils
{
    private static Map<Integer,String> keyMap=new HashMap<>(){{
        put(0,"MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQChd4T6x/6H+Kos2Amgcr3+LbNGuP8AYu0QwpOrpJpusTzVrRvtXoBR8+SXO9uKlymNQ7X+BTh79LlGxeYX0LvPjBtcIcw3SFNVBsLb1EhXTN1inaODEDnubkbnE9HiAPBRU0Zdr8RPM7a5CVxIohdX4V6tPdhcXOOHkLJDUyX5BwIDAQAB");
        put(1,"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");
    }};



    public RSAUtils(){

    }

    /**
     * 随机生成密钥对
     * @throws NoSuchAlgorithmException
     */
    public static void getKeyPair() throws Exception {
        //KeyPairGenerator类用于生成公钥和密钥对，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();
        PrivateKey privateKey = keyPair.getPrivate();//得到私钥
        PublicKey publicKey = keyPair.getPublic();//得到公钥
        //得到公钥字符串
        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(0,publicKeyString);//0表示公钥
        keyMap.put(1,privateKeyString);//1表示私钥
        System.out.println(keyMap);
    }
    /**
     * RSA公钥加密
     *
     * @param str
     *            加密字符串
     *
     *            公钥
     * @return 密文
     * @throws Exception
     *             加密过程中的异常信息
     */
    public static String encrypt(String str) throws Exception {
        //base64编码的公钥
        byte[] decoded = Base64.decodeBase64(keyMap.get(0));
        RSAPublicKey pubKey= (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(decoded));
        //RAS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;
    }

    /**
     * RSA私钥解密
     *
     * @param str
     *            加密字符串
     *
     *            私钥
     * @return 铭文
     * @throws Exception
     *             解密过程中的异常信息
     */
    public static String decrypt(String str) throws Exception {
        //Base64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(keyMap.get(1));
        PrivateKey priKey = 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;

    }
}

调用RSA加密算法模块。

public static void main(String[] args) {
        try {
            //生成公钥和私钥
            RSAUtils.getKeyPair();
            //加密字符串
            String password="Jianfreespace";
            String outstr = RSAUtils.encrypt(password);
            String deoutstr = RSAUtils.decrypt(outstr);
            System.out.println(outstr);
            System.out.println(deoutstr);
            InetAddress addr = InetAddress.getLocalHost();
            System.out.println("Local HostAddress: "+addr.getHostAddress());
            String hostname = addr.getHostName();
            System.out.println("Local host name: "+hostname);
        }catch (Exception e){
            System.out.println(e);
        }

    }