RSA加解密及分段加解密

Posted 2022-12-01 陳英傑

package com.xxx;

import android.util.Base64;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.security.InvalidKeyException;
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.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;

/**
 * create by chenyingjie on 2020/3/30
 * desc
 */
public class RSAUtil 

    private static final String PUB_K = "";

    private static final Charset CHARSET = StandardCharsets.UTF_8;
    private static final String RSA = "RSA";
    private static final String RSA_ECB = "RSA/ECB/PKCS1Padding";

    /**
     * 随机生成密钥对
     */
    public static void getKeyPair() 
        try 
            // 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 = Base64.encodeToString(publicKey.getEncoded(), Base64.DEFAULT);
            // 得到私钥字符串
            String privateKeyString = Base64.encodeToString(privateKey.getEncoded(), Base64.DEFAULT);
            // 将公钥和私钥打印
            
         catch (NoSuchAlgorithmException e) 
            e.printStackTrace();
        
    

    public static String encryptParams(String str) 
        return rsaEncode(str, PUB_K);
    

	/**
	 * 简单字符串加密
	 */
    public static String encryptSimple(String str, String publicKey) 
        try 
            //base64编码的公钥
            byte[] decoded = Base64.decode(publicKey, Base64.DEFAULT);
            RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance(RSA).generatePublic(new X509EncodedKeySpec(decoded));
            //RSA加密
            Cipher cipher = Cipher.getInstance(RSA_ECB);
            cipher.init(Cipher.ENCRYPT_MODE, pubKey);
            String outStr = Base64.encodeToString(cipher.doFinal(str.getBytes(CHARSET)), Base64.DEFAULT);
            return outStr;
         catch (NoSuchAlgorithmException e) 
            e.printStackTrace();
         catch (NoSuchPaddingException e) 
            e.printStackTrace();
         catch (InvalidKeySpecException e) 
            e.printStackTrace();
         catch (InvalidKeyException e) 
            e.printStackTrace();
         catch (BadPaddingException e) 
            e.printStackTrace();
         catch (IllegalBlockSizeException e) 
            e.printStackTrace();
        
        return "";
    

	/**
	 * 简单字符串解密
	 */
    public static String decryptSimple(String str, String privateKey) 
        try 
            //64位解码加密后的字符串
            byte[] inputByte = Base64.decode(str.getBytes(CHARSET), Base64.DEFAULT);
            //base64编码的私钥
            byte[] decoded = Base64.decode(privateKey, Base64.DEFAULT);
            RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance(RSA).generatePrivate(new PKCS8EncodedKeySpec(decoded));
            //RSA解密
            Cipher cipher = Cipher.getInstance(RSA_ECB);
            cipher.init(Cipher.DECRYPT_MODE, priKey);
            String outStr = new String(cipher.doFinal(inputByte));
            return outStr;
         catch (NoSuchAlgorithmException e) 
            e.printStackTrace();
         catch (NoSuchPaddingException e) 
            e.printStackTrace();
         catch (InvalidKeySpecException e) 
            e.printStackTrace();
         catch (InvalidKeyException e) 
            e.printStackTrace();
         catch (BadPaddingException e) 
            e.printStackTrace();
         catch (IllegalBlockSizeException e) 
            e.printStackTrace();
        
        return "";
    

    /**
     * 解密内容过长需要使用分段加密
     *
     * @return String
     */
    public static String rsaEncode(String data, String publicKey) 
        byte[] b = data.getBytes();
        try (ByteArrayOutputStream out = new ByteArrayOutputStream()) 
            byte[] decoded = Base64.decode(publicKey, Base64.DEFAULT);
            RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance(RSA).generatePublic(new X509EncodedKeySpec(decoded));
            int keySize = pubKey.getModulus().bitLength();
            int maxBlock = keySize / 8 - 11;

            int inputLen = b.length;
            int offSet = 0;
            byte[] cache;
            int i = 0;
            Cipher cipher = Cipher.getInstance(RSA_ECB);
            cipher.init(Cipher.ENCRYPT_MODE, pubKey);
            // 对数据分段解密
            while (inputLen - offSet > 0) 
                if (inputLen - offSet > maxBlock) 
                    cache = cipher.doFinal(b, offSet, maxBlock);
                 else 
                    cache = cipher.doFinal(b, offSet, inputLen - offSet);
                
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * maxBlock;
            
            byte[] decryptedData = out.toByteArray();
            return Base64.encodeToString(decryptedData, Base64.DEFAULT);
         catch (IOException e) 
            e.printStackTrace();
         catch (NoSuchAlgorithmException e) 
            e.printStackTrace();
         catch (InvalidKeySpecException e) 
            e.printStackTrace();
         catch (NoSuchPaddingException e) 
            e.printStackTrace();
         catch (InvalidKeyException e) 
            e.printStackTrace();
         catch (IllegalBlockSizeException e) 
            e.printStackTrace();
         catch (BadPaddingException e) 
            e.printStackTrace();
        
        return "";
    

    /**
     * 分段解密
     *
     * @return String
     */
    public static String rsaDecode(String data, String privateKey) 
        try (ByteArrayOutputStream out = new ByteArrayOutputStream()) 
            byte[] decoded = Base64.decode(privateKey, Base64.DEFAULT);
            RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance(RSA).generatePrivate(new PKCS8EncodedKeySpec(decoded));
            int keySize = priKey.getModulus().bitLength();
            int maxBlock = keySize / 8;

            byte[] b = Base64.decode(data.getBytes(CHARSET), Base64.URL_SAFE);
            int inputLen = b.length;
            int offSet = 0;
            byte[] cache;
            int i = 0;
            Cipher cipher = Cipher.getInstance(RSA_ECB);
            cipher.init(Cipher.DECRYPT_MODE, priKey);
            // 对数据分段解密
            while (inputLen - offSet > 0) 
                if (inputLen - offSet > maxBlock) 
                    cache = cipher.doFinal(b, offSet, maxBlock);
                 else 
                    cache = cipher.doFinal(b, offSet, inputLen - offSet);
                
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * maxBlock;
            
            byte[] decryptedData = out.toByteArray();
            return new String(decryptedData);
         catch (NoSuchAlgorithmException e) 
            e.printStackTrace();
         catch (InvalidKeySpecException e) 
            e.printStackTrace();
         catch (UnsupportedEncodingException e) 
            e.printStackTrace();
         catch (NoSuchPaddingException e) 
            e.printStackTrace();
         catch (InvalidKeyException e) 
            e.printStackTrace();
         catch (IllegalBlockSizeException e) 
            e.printStackTrace();
         catch (BadPaddingException e) 
            e.printStackTrace();
         catch (IOException e) 
            e.printStackTrace();
        
        return "";