关于RAS加密解密的一个文章，看着一个就够了！！！

RAS在网上看了太多文章很多都是不全的，复制过去各种问题，所有就有写个博客的想法，一是方便大家，二是方便自己,好了废话不多说了!

首先要注意一下证书级别

1024位的证书，加密时最大支持117个字节，解密时为128；

2048位的证书，加密时最大支持245个字节，解密时为256。

创建RAS工具类

package club.loserblog.blogreception.util;

import org.apache.tomcat.util.http.fileupload.ByteArrayOutputStream;
import sun.misc.BASE64Decoder;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import java.io.IOException;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;

/**
 * @ClassName RsaUtil
 * @Description TODO
 * @Author loser
 * @Date 2020/4/12 18:26
 **/
public class RsaUtil {
    private PublicKey commonKey;

    private PrivateKey secrecyKey;

    /*
    * 1024位的证书，加密时最大支持117个字节，解密时为128；
    * 2048位的证书，加密时最大支持245个字节，解密时为256。
    * */

    /**
     * @Author: dingmingming
     * @Description: 初始化公钥和密钥
     * @Date: 2020/4/12 18:37
     * @Param:
     * @Return:
     **/
    public RsaUtil() throws GeneralSecurityException{
        KeyPairGenerator pairGenerator = KeyPairGenerator.getInstance("RSA");
        pairGenerator.initialize(1024);
        KeyPair keyPair = pairGenerator.generateKeyPair();
        this.commonKey = keyPair.getPublic();
        this.secrecyKey = keyPair.getPrivate();
    }

    /**
     * @Author: dingmingming
     * @Description: 恢复公钥和密钥
     * @Date: 2020/4/12 18:37
     * @Param:
     * @Return:
     **/
    public RsaUtil(byte[] commonKey,byte[] secrecyKey)  throws GeneralSecurityException{
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(commonKey);
        this.commonKey = keyFactory.generatePublic(x509EncodedKeySpec);
        PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(secrecyKey);
        this.secrecyKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
    }

    /**
     * @Author: dingmingming
     * @Description: 将公钥转换为字节
     * @Date: 2020/4/12 18:39
     * @Param:
     * @Return:
     **/
    public byte[] getCommonKey(){
        return commonKey.getEncoded();
    }

    /**
     * @Author: dingmingming
     * @Description: 将私钥转换为字节
     * @Date: 2020/4/12 18:39
     * @Param:
     * @Return:
     **/
    public byte[] getSecrecyKey(){
        return secrecyKey.getEncoded();
    }

    /**
     * @Author: dingmingming
     * @Description: 利用公钥加密
     * @Date: 2020/4/12 18:45
     * @Param:
     * @Return:
     **/
    public String encryptStr(String encryptStr) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException, IOException {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(1, this.commonKey);
        byte[] result = encryptStr.getBytes();
        int inputLen = result.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;

        for(int i = 0; inputLen - offSet > 0; offSet = i * 117) {
            byte[] cache;
            if(inputLen - offSet > 117) {
                cache = cipher.doFinal(result, offSet, 117);
            } else {
                cache = cipher.doFinal(result, offSet, inputLen - offSet);
            }

            out.write(cache, 0, cache.length);
            ++i;
        }

        byte[] encryptedData = out.toByteArray();
        out.close();
        String encryptData = Base64.getEncoder().encodeToString(encryptedData);
        return encryptData;
    }

    /**
     * @Author: dingmingming
     * @Description: 利用私钥解密
     * @Date: 2020/4/12 18:45
     * @Param:
     * @Return:
     **/
    public String decryptStr(String decryptStr) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException, IOException {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(2, secrecyKey);
        byte[] result = new BASE64Decoder().decodeBuffer(decryptStr);
        int inputLen = result.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;

        for(int i = 0; inputLen - offSet > 0; offSet = i * 128) {
            byte[] cache;
            if(inputLen - offSet > 128) {
                cache = cipher.doFinal(result, offSet, 128);
            } else {
                cache = cipher.doFinal(result, offSet, inputLen - offSet);
            }

            out.write(cache, 0, cache.length);

            ++i;
        }

        byte[] decryptedData = out.toByteArray();
        out.close();
        String decryptData = new String(decryptedData,"UTF-8");
        return decryptData;
    }

}
           

获取前端数据处理

public ModelAndView getBlogInfoForLook(HttpServletRequest request) throws IllegalBlockSizeException, InvalidKeyException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException, IOException {
        //blogId 代表的是前端的参数名称 这个大家应该都了解
        String blogId = request.getParameter("blogId").trim();
        //这里是重点要注意的 一定要替换
        //为什么要替换 因为参数传递的过程中 会将加密字符中的加号变成空格，因此我们需要将其替换回来 避免解密失败
        blogId = blogId.replaceAll(" ","+");

        //可以进行揭秘操作了
}
           

前端这一块我只是重点说一下解密 ，因为解密猜的坑有点多，加密都没有什么问题调用方法就行

好了就这样了！！！