java RSA公钥加密私钥解密

Myth丶恋晨 2021-12-23 15:39 413阅读 0赞

RSA非对称加密原理此处不是重点,麻烦读者自行了解哦。如果了解了RSA，你就知道为什么要用公钥加密,私钥解密(不懂私聊哦),下面是RSA加解密例子，RSA加解密算法有好多种，这是常见也是比较简单的一种。

package com.alipay;
    
    import cn.paypalm.commons.util.Logger;
    import cn.paypalm.commons.util.LoggerFactory;
    import org.apache.commons.codec.binary.Base64;
    import javax.crypto.Cipher;
    import java.io.BufferedReader;
    import java.io.ByteArrayOutputStream;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    import java.security.KeyFactory;
    import java.security.PrivateKey;
    import java.security.PublicKey;
    import java.security.cert.CertificateFactory;
    import java.security.spec.PKCS8EncodedKeySpec;
    import java.security.spec.X509EncodedKeySpec;
    
    /**
     * Created by lifeng on 2019/6/25.
     */
    public class RSAUtil {
        private static final Logger LOGGER= LoggerFactory.getLogger(RSAUtil.class);
        /**
         * RSA最大加密明文大小
         */
        private static final int MAX_ENCRYPT_BLOCK = 117;
        /**
         * RSA最大解密密文大小（如果秘钥是1024bit,解密最大块是128,如果秘钥是2048bit,解密最大块是256）
         */
        private static final int MAX_DECRYPT_BLOCK = 128;
        private static PrivateKey globalPrivateKey = null;
        private static PublicKey globalPublicKey = null;
    
        public static PrivateKey getPrivateKey(String prikeypath) throws Exception {
            if(globalPrivateKey != null){
                return globalPrivateKey;
            }
            InputStream in = RSAUtil.class.getClassLoader().getResourceAsStream(prikeypath);
            BufferedReader br = new BufferedReader(new InputStreamReader(in));
            StringBuilder sb = new StringBuilder();
            String readLine = null;
    
            while((readLine = br.readLine()) != null) {
                if(readLine.charAt(0) != 45) {
                    sb.append(readLine);
                    sb.append('\r');
                }
            }
    
            in.close();
            PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(Base64.decodeBase64(sb.toString()));
            try {
                KeyFactory factory = KeyFactory.getInstance("RSA");
                PrivateKey privateKey = factory.generatePrivate(pkcs8EncodedKeySpec);
                globalPrivateKey = privateKey;
                return globalPrivateKey;
            } catch (Exception e) {
                LOGGER.error("获取私钥异常",e);
                throw e;
            }
        }
    
        public static PublicKey getPublicByPublic(String keypath) throws Exception {
            if(globalPublicKey != null){
                return globalPublicKey;
            }
            InputStream in = RSAUtil.class.getClassLoader().getResourceAsStream(keypath);
            BufferedReader br = new BufferedReader(new InputStreamReader(in));
            StringBuilder sb = new StringBuilder();
            String readLine = null;
    
            while((readLine = br.readLine()) != null) {
                if(readLine.charAt(0) != 45) {
                    sb.append(readLine);
                    sb.append('\r');
                }
            }
    
            in.close();
            CertificateFactory certificateFactory = CertificateFactory.getInstance("X.509");
            X509EncodedKeySpec ks = new X509EncodedKeySpec(Base64.decodeBase64(sb.toString()));
            KeyFactory kf = KeyFactory.getInstance("RSA");
            globalPublicKey = kf.generatePublic(ks);
            return globalPublicKey;
        }
    
        public static String dencrypt(String str,String privateKeyStr) throws Exception{
            //64位解码加密后的字符串
            byte[] encryptedData = Base64.decodeBase64(str.getBytes("UTF-8"));
            PrivateKey privateKey = getPrivateKey(privateKeyStr);
            //RSA加密
            Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.DECRYPT_MODE, privateKey);
            int inputLen = encryptedData.length;
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            int offSet = 0;
            byte[] cache;
            int i = 0;
            // 对数据分段解密
            while (inputLen - offSet > 0) {
                if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                    cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
                } else {
                    cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
                }
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * MAX_DECRYPT_BLOCK;
            }
            byte[] decryptedData = out.toByteArray();
            out.close();
            String outStr = new String(decryptedData,"UTF-8");
            return outStr;
        }
    
        public static String encrypt(String data, String publicKeyPath) throws Exception{
            PublicKey pubKey = getPublicByPublic(publicKeyPath);
            //RSA加密
            Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.ENCRYPT_MODE, pubKey);
            byte[] dataByte = data.getBytes("UTF-8");
            int inputLen = dataByte.length;
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            int offSet = 0;
            byte[] cache;
            int i = 0;
            // 对数据分段加密
            while (inputLen - offSet > 0) {
                if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                    cache = cipher.doFinal(dataByte, offSet, MAX_ENCRYPT_BLOCK);
                } else {
                    cache = cipher.doFinal(dataByte, offSet, inputLen - offSet);
                }
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * MAX_ENCRYPT_BLOCK;
            }
            byte[] encryptedData = out.toByteArray();
            out.close();
    
            String outStr = Base64.encodeBase64String(encryptedData);
            return outStr;
        }
    
        public static void main(String[] args) throws Exception {
            //现在生成公私钥对,http://web.chacuo.net/netrsakeypair
            String data = "我是打酱油的";
            //使用公钥加密,第二个参数classpath下的公钥文件
            data = encrypt(data,"public1024.key");
            System.out.println("加密后的数据:"+data);
            //使用私钥解密,第二个参数classpath下的私钥文件
            data = dencrypt(data,"private1024.key");
            System.out.println("解密后的数据:"+data);
        }
    }

## 生成公私钥对,[http://web.chacuo.net/netrsakeypair][http_web.chacuo.net_netrsakeypair]   ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTA1MDkwNTI_size_16_color_FFFFFF_t_70] ##

同时给你读者推荐一个好用在线加解密的网站,你会喜欢的。  
[http://tool.chacuo.net/cryptdes][http_tool.chacuo.net_cryptdes]  
[http://encode.chahuo.com/][http_encode.chahuo.com]

[http_web.chacuo.net_netrsakeypair]: http://web.chacuo.net/netrsakeypair
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTA1MDkwNTI_size_16_color_FFFFFF_t_70]: /images/20211223/1984e7d8d37841998bd57b827f3f6217.png
[http_tool.chacuo.net_cryptdes]: http://tool.chacuo.net/cryptdes
[http_encode.chahuo.com]: http://encode.chahuo.com/