Java 加密技术

女爷i 2024-04-19 08:45 65阅读 0赞

###### Java加密算法 ######

JDK中带有部分加密算法的实现类，主要的是java.security和javax.crypto包下的类，还可以使用Bouncy Castle（丰富JDK中加密算法的不足）jar包是：bcprov-jdk15on-1.57.jar和Commons Codec（简化JDK中加密的操作）jar包是：commons-codec-1.10.jar

###### Base64 ######

Base64用于网络中传输的数据进行编码，严格意义上属于编码的格式，有64个字符的对应的编码，Base64就是将内容按照该格式进行编码。可以对数据编码和解码，是可逆的，安全度较低，不过，也可以作为最基础最简单的加密算法用于加密要求较弱的情况

Base64可以使用JDk中自带的类实现，还可以使用Bouncy Castle（简称bc）或Commons Codec（简称cc）实现

加密数据：

private static String src="Hello Base64";

导入的类：

import java.io.IOException;
    
    import org.apache.commons.codec.binary.Base64;
    
    import sun.misc.BASE64Decoder;
    import sun.misc.BASE64Encoder;

JDk实现主要使用用BASE64Encoder和BASE64Decoder类的方法（注意：在Eclipse中使用JDK的Base64可能会出现找不到的问题，是因为Base64Encoder并不属于JDK标准库范畴，但是又包含在了JDK中，需要我们手动导入\\jre\\lib目录下的rt.jar包即可）：

public static void jdkBase64(){
        
            try {
        
                BASE64Encoder encoder=new BASE64Encoder();
                String encode = encoder.encode(src.getBytes());
                System.out.println("encode: "+encode);
                
                BASE64Decoder decoder=new BASE64Decoder();
                String decode=new String(decoder.decodeBuffer(encode));
                System.out.println("decode: "+decode);
            } catch (IOException e) {
        
                e.printStackTrace();
            }
        }

bc实现主要是用Base64类的方法：

public static void bouncybastleBase64(){
        
            byte[] encode = org.bouncycastle.util.encoders.Base64.encode(src.getBytes());
            System.out.println("encode: "+new String(encode));
            
            byte[] decode = org.bouncycastle.util.encoders.Base64.decode(encode);
            System.out.println("decode: "+new String(decode));
        }

cc实现也是用Base64类，不过与bc的是不一样的，不同包中的类，只是名字一样：

public static void commonscodecBase64(){
        
            byte[] encode=Base64.encodeBase64(src.getBytes());
            System.out.println("encode: "+new String(encode));  //需要转化为String
            
            byte[] decode = Base64.decodeBase64(encode);
            System.out.println("decode: "+new String(decode));
        }

###### 摘要算法 ######

摘要算法主要分为MD，SHA和Hmac算法，摘要算法其实是用于效验数据完整性的，我们在下载某些文件时，会有MD5和SHA1值提供我们效验下载的文件是否完整，可以用于根据数据生成其唯一的摘要值，无法根据摘要值知道原数据，属于不可逆的

###### MD： ######

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly92dmNhdC5ibG9nLmNzZG4ubmV0_size_16_color_FFFFFF_t_70]

加密数据：

private static String src="Hello MD";

导入的类：

import java.security.MessageDigest;
    import java.security.NoSuchAlgorithmException;
    import java.security.Provider;
    import java.security.Security;
    
    import org.apache.commons.codec.binary.Hex;
    import org.apache.commons.codec.digest.DigestUtils;
    import org.bouncycastle.crypto.Digest;
    import org.bouncycastle.crypto.digests.MD2Digest;
    import org.bouncycastle.crypto.digests.MD4Digest;
    import org.bouncycastle.crypto.digests.MD5Digest;
    import org.bouncycastle.jce.provider.BouncyCastleProvider;

JDK有MD2和MD5的实现，使用的是MessageDigest类，而没有MD4的实现：

public static void jdkMD5(){
        
            try {
        
                MessageDigest md=MessageDigest.getInstance("MD5");
                byte[] digest = md.digest(src.getBytes());
                System.out.println("JDK MD5: "+Hex.encodeHexString(digest));           //使用的是cc中带的Hex需要转换为十六进制
            } catch (NoSuchAlgorithmException e) {
        
                e.printStackTrace();
            }
            
        }
        
        public static void jdkMD2(){
        
            try {
        
                MessageDigest md=MessageDigest.getInstance("MD2");
                byte[] digest = md.digest(src.getBytes());
                System.out.println("JDK MD2: "+Hex.encodeHexString(digest));   
            } catch (NoSuchAlgorithmException e) {
        
                e.printStackTrace();
            }
            
        }

而bc这三种都有，使用的是Digest 类：

public static void bcMD4(){
        
            //方式一
    //        Digest digest=new MD4Digest();
    //        digest.update(src.getBytes(), 0, src.getBytes().length);
    //        byte[] md4Bytes=new byte[digest.getDigestSize()];
    //        digest.doFinal(md4Bytes, 0);
    //        System.out.println("BC MD4: "+org.bouncycastle.util.encoders.Hex.toHexString(md4Bytes));
            
            
          //方式二(通过添加provider的方式，将sun的改为bc的provider)
            try {
        
                Security.addProvider(new BouncyCastleProvider());  //通过添加provider的方式
                MessageDigest md=MessageDigest.getInstance("MD4");
                byte[] digest = md.digest(src.getBytes());
                System.out.println("BC MD4: "+Hex.encodeHexString(digest));
            } catch (NoSuchAlgorithmException e) {
        
                e.printStackTrace();
            }
        }
        
        public static void bcMD5(){
        
            Digest digest=new MD5Digest();
            digest.update(src.getBytes(), 0, src.getBytes().length);
            byte[] md4Bytes=new byte[digest.getDigestSize()];
            digest.doFinal(md4Bytes, 0);
            System.out.println("BC MD5: "+org.bouncycastle.util.encoders.Hex.toHexString(md4Bytes));
        }
        
        public static void bcMD2(){
        
            Digest digest=new MD2Digest();
            digest.update(src.getBytes(), 0, src.getBytes().length);
            byte[] md4Bytes=new byte[digest.getDigestSize()];
            digest.doFinal(md4Bytes, 0);
            System.out.println("BC MD2: "+org.bouncycastle.util.encoders.Hex.toHexString(md4Bytes));
        }

cc和JDK是一样的，毕竟是对JDK加密的简化，直接使用DigestUtils中的方法，很简单，而且前两种方法还需要将MD值转换为十六进制，cc直接就帮我们转了：

public static void ccMD2(){
                //有方法直接就可以转换十六进制
            System.out.println("CC MD2: "+DigestUtils.md2Hex(src.getBytes()));
        }
        
        public static void ccMd5(){
        
            System.out.println("CC MD5: "+DigestUtils.md5Hex(src.getBytes()));
        }

###### SHA： ######

这里只是使用SHA-1，其他类型类似  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly92dmNhdC5ibG9nLmNzZG4ubmV0_size_16_color_FFFFFF_t_70 1]

加密数据：

private static String src="Hello SHA";

要导入的类：

import java.security.MessageDigest;
    import java.security.NoSuchAlgorithmException;
    
    import org.apache.commons.codec.binary.Hex;
    import org.apache.commons.codec.digest.DigestUtils;
    import org.bouncycastle.crypto.Digest;
    import org.bouncycastle.crypto.digests.SHA1Digest;import sun.security.provider.SHA;

JDK实现方式（同样是使用MessageDigest）：

public static void jdkSHA1(){
        
            MessageDigest digest;
            try {
        
                digest = MessageDigest.getInstance("SHA");
                digest.update(src.getBytes());
                System.out.println("JDK SHA1: "+Hex.encodeHexString(digest.digest()));
            } catch (NoSuchAlgorithmException e) {
        
                e.printStackTrace();
            }
        }

bc的实现方式（同样是Digest 类）：

public static void mcSHA1(){
        
            Digest digest=new SHA1Digest();
            digest.update(src.getBytes(),0,src.getBytes().length);
            byte[] sha1Byte1=new byte[digest.getDigestSize()];
            digest.doFinal(sha1Byte1, 0);
            System.out.println("MC SHA1:"+org.bouncycastle.util.encoders.Hex.toHexString(sha1Byte1));
        }

cc的实现方式：

public static void ccsha(){
        
            System.out.println("CC sha1:"+DigestUtils.sha1Hex(src));
        }

###### Hmac（含有密钥的摘要算法，也有简称mac，密钥不同摘要也不同）： ######

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly92dmNhdC5ibG9nLmNzZG4ubmV0_size_16_color_FFFFFF_t_70 2]  
要加密的数据：

private static String src="Hello HMAC";

要导入的类：

import javax.crypto.KeyGenerator;
    import javax.crypto.Mac;
    import javax.crypto.SecretKey;
    import javax.crypto.spec.SecretKeySpec;
    
    import org.apache.commons.codec.binary.Hex;
    import org.bouncycastle.crypto.digests.MD5Digest;
    import org.bouncycastle.crypto.macs.HMac;
    import org.bouncycastle.crypto.params.KeyParameter;

JDK的实现方式：

public static void jdkHmacMD5(){
        
            try {
        
                KeyGenerator keyGenerator=KeyGenerator.getInstance("HmacMD5");  //初始化KeyGenerator
                SecretKey secretKey=keyGenerator.generateKey(); //产生密钥
                //byte[] key=secretKey.getEncoded();     //获得密钥(默认生成)
                
                byte[] key=Hex.decodeHex(new char[]{
        'a','a','a','a','a','a','a','a','a','a'});  //手动生成密钥(十位)
                
                SecretKey secretKey2=new SecretKeySpec(key, "HmacMD5"); //还原密钥
                Mac mac=Mac.getInstance(secretKey2.getAlgorithm());  //实例化mac
                //初始化mac
                mac.init(secretKey2);
                byte[] hmacMD5Bytes=mac.doFinal(src.getBytes());
                System.out.println("jdk hmacMD5: "+Hex.encodeHexString(hmacMD5Bytes));
            } catch (Exception e) {
        
                e.printStackTrace();
            } 
        }

bc的实现方式：

public static void bcHmacMd5(){
        
            HMac hMac=new HMac(new MD5Digest());
            hMac.init(new KeyParameter(org.bouncycastle.util.encoders.Hex.decode("aaaaaaaaaa")));  //需要十位密钥
            hMac.update(src.getBytes(),0,src.getBytes().length);
            
            byte[] hmacMD5=new byte[hMac.getMacSize()];
            hMac.doFinal(hmacMD5, 0);
            System.out.println("bc hmacMD5: "+org.bouncycastle.util.encoders.Hex.toHexString(hmacMD5));
    
        }

###### 对称加密算法 ######

严格意义上的加密算法，分为对称和非对称加密算法，所谓对称是说发送方和接收方的密钥是一样的，而非对称我们后面再说。因为密钥一样所以安全性跟非对称比较来说就不太安全了

对称加密算法主要分为:DES , 3DES(3重DES) , AES(想要替代DES) , PBE(基于口令的对称算法)

###### DES: ######

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly92dmNhdC5ibG9nLmNzZG4ubmV0_size_16_color_FFFFFF_t_70 3]  
加密数据 :

private static String src="Hello DES";

导入的类：

import java.security.Security;
    
    import javax.crypto.Cipher;
    import javax.crypto.KeyGenerator;
    import javax.crypto.SecretKey;
    import javax.crypto.SecretKeyFactory;
    import javax.crypto.spec.DESKeySpec;
    
    import org.apache.commons.codec.binary.Hex;
    import org.bouncycastle.jce.provider.BouncyCastleProvider;

JDK的实现方式：

public static void jdkDES(){
        
            try {
        
                //生成key
                KeyGenerator keyGenerator=KeyGenerator.getInstance("DES");
                keyGenerator.init(56);      //指定key长度，同时也是密钥长度(56位)
                SecretKey secretKey = keyGenerator.generateKey(); //生成key的材料
                byte[] key = secretKey.getEncoded();  //生成key
                
                //key转换成密钥
                DESKeySpec desKeySpec=new DESKeySpec(key);
                SecretKeyFactory factory=SecretKeyFactory.getInstance("DES");
                SecretKey key2 = factory.generateSecret(desKeySpec);      //转换后的密钥
                
                //加密
                Cipher cipher=Cipher.getInstance("DES/ECB/PKCS5Padding");  //算法类型/工作方式/填充方式
                cipher.init(Cipher.ENCRYPT_MODE, key2);   //指定为加密模式
                byte[] result=cipher.doFinal(src.getBytes());
                System.out.println("jdkDES加密: "+Hex.encodeHexString(result));  //转换为十六进制
                
                //解密
                cipher.init(Cipher.DECRYPT_MODE,key2);  //相同密钥，指定为解密模式
                result = cipher.doFinal(result);   //根据加密内容解密
                System.out.println("jdkDES解密: "+new String(result));  //转换字符串
                
            } catch (Exception e) {
        
                e.printStackTrace();
            }
        }

bc的实现方式，为了和JDK的实现方式一致（不想记太多类）,采用了添加provider的方式 :

public static void bcDES(){
        
            try {
        
                //通过改变provider的方式
                Security.addProvider(new BouncyCastleProvider());
                
                //生成key,使用bc需要在后面指定"BC"
                KeyGenerator keyGenerator=KeyGenerator.getInstance("DES","BC");
                
                keyGenerator.getProvider();
                
                keyGenerator.init(56);      //指定key长度，同时也是密钥长度
                SecretKey secretKey = keyGenerator.generateKey(); //生成key的材料
                byte[] key = secretKey.getEncoded();  //生成key
                
                //key转换成密钥
                DESKeySpec desKeySpec=new DESKeySpec(key);
                SecretKeyFactory factory=SecretKeyFactory.getInstance("DES");
                SecretKey key2 = factory.generateSecret(desKeySpec);      //转换后的密钥
                
                //加密
                Cipher cipher=Cipher.getInstance("DES/ECB/PKCS5Padding");  //算法类型/工作方式/填充方式
                cipher.init(Cipher.ENCRYPT_MODE, key2);
                byte[] result=cipher.doFinal(src.getBytes());
                System.out.println("bcDES加密: "+Hex.encodeHexString(result));  //转换为十六进制
                
                //解密
                cipher.init(Cipher.DECRYPT_MODE,key2);  //相同密钥
                result = cipher.doFinal(result);   //根据加密内容解密
                System.out.println("bcDES解密: "+new String(result));  //转换字符串
                
            } catch (Exception e) {
        
                e.printStackTrace();
            }
        }

就是记得添加bc的provider，和KeyGenerator.getInstance的参数(“DES”,“BC”)

###### 3DES（使用DESede作为标识）： ######

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly92dmNhdC5ibG9nLmNzZG4ubmV0_size_16_color_FFFFFF_t_70 4]  
要加密的数据：

private static String src="Hello 3DES";

导入的类：

import java.security.SecureRandom;
    import java.security.Security;
    
    import javax.crypto.Cipher;
    import javax.crypto.KeyGenerator;
    import javax.crypto.SecretKey;
    import javax.crypto.SecretKeyFactory;
    import javax.crypto.spec.DESedeKeySpec;
    
    import org.apache.commons.codec.binary.Hex;
    import org.bouncycastle.jce.provider.BouncyCastleProvider;

JDK的实现方法：

public static void jdkDES(){
        
            try {
        
                //生成key
                KeyGenerator keyGenerator=KeyGenerator.getInstance("DESede");
                //keyGenerator.init(112);      //3DES需要112 or 168位
                keyGenerator.init(new SecureRandom());   //或者使用这种方式默认长度，无需指定长度
                SecretKey secretKey = keyGenerator.generateKey(); //生成key的材料
                byte[] key = secretKey.getEncoded();  //生成key
                
                //key转换成密钥
                DESedeKeySpec desKeySpec=new DESedeKeySpec(key);
                SecretKeyFactory factory=SecretKeyFactory.getInstance("DESede");
                SecretKey key2 = factory.generateSecret(desKeySpec);      //转换后的密钥
                
                //加密
                Cipher cipher=Cipher.getInstance("DESede/ECB/PKCS5Padding");  //算法类型/工作方式/填充方式
                cipher.init(Cipher.ENCRYPT_MODE, key2);   //指定为加密模式
                byte[] result=cipher.doFinal(src.getBytes());
                System.out.println("jdk3DES加密: "+Hex.encodeHexString(result));  //转换为十六进制
                
                //解密
                cipher.init(Cipher.DECRYPT_MODE,key2);  //相同密钥，指定为解密模式
                result = cipher.doFinal(result);   //根据加密内容解密
                System.out.println("jdk3DES解密: "+new String(result));  //转换字符串
                
            } catch (Exception e) {
        
                e.printStackTrace();
            }
        }

bc的实现方式：

public static void bcDES(){
        
            try {
        
                //通过改变provider的方式，其他操作一样
                Security.addProvider(new BouncyCastleProvider());
                
                //生成key
                KeyGenerator keyGenerator=KeyGenerator.getInstance("DESede");
                keyGenerator.init(new SecureRandom());
                SecretKey secretKey = keyGenerator.generateKey(); //生成key的材料
                byte[] key = secretKey.getEncoded();  //生成key
                
                //key转换成密钥
                DESedeKeySpec desKeySpec=new DESedeKeySpec(key);
                SecretKeyFactory factory=SecretKeyFactory.getInstance("DESede");
                SecretKey key2 = factory.generateSecret(desKeySpec);      //转换后的密钥
                
                //加密
                Cipher cipher=Cipher.getInstance("DESede/ECB/PKCS5Padding");  //算法类型/工作方式/填充方式
                cipher.init(Cipher.ENCRYPT_MODE, key2);   //指定为加密模式
                byte[] result=cipher.doFinal(src.getBytes());
                System.out.println("jdk3DES加密: "+Hex.encodeHexString(result));  //转换为十六进制
                
                //解密
                cipher.init(Cipher.DECRYPT_MODE,key2);  //相同密钥，指定为解密模式
                result = cipher.doFinal(result);   //根据加密内容解密
                System.out.println("jdk3DES解密: "+new String(result));  //转换字符串
                
            } catch (Exception e) {
        
                e.printStackTrace();
            }
        }

###### AES: ######

![在这里插入图片描述][20190916104208640.jpg]  
基本实现和DES类似，只不过在实现该算法的时候，设置密钥长度大于128会出现错误：Illegal key size or default parameters，这是因为美国的出口限制，Sun通过权限文件（local\_policy.jar、US\_export\_policy.jar）做了相应限制，Oracle在其官方网站上提供了无政策限制权限文件（Unlimited Strength Jurisdiction Policy Files），我们只需要将其部署在JRE环境中，就可以解决限制问题

JDK8的无政策限制权限文件（http://www.oracle.com/technetwork/java/javase/downloads/jce8-download-2133166.html）

将下载的local\_policy.jar和US\_export\_policy.jar替换JDK的JRE环境中，或者是JRE环境中上述两个jar文件即可

非对称的ELGamal加密算法算法也有该问题，解决方法相同

加密的数据：

private static String src="Hello AES";

导入的类：

import java.security.Key;
    import java.security.SecureRandom;
    import java.security.Security;
    import javax.crypto.Cipher;
    import javax.crypto.KeyGenerator;
    import javax.crypto.SecretKey;
    import javax.crypto.spec.SecretKeySpec;
    import org.apache.commons.codec.binary.Hex;
    import org.bouncycastle.jce.provider.BouncyCastleProvider;

JDK的实现：

public static void jdkAES(){
        
            try {
        
                //生成key
                KeyGenerator keyGenerator=KeyGenerator.getInstance("AES");
                keyGenerator.init(new SecureRandom());
                SecretKey secretKey = keyGenerator.generateKey();
                byte[] key1 = secretKey.getEncoded();
                
                //key转换为密钥
                Key key2 = new SecretKeySpec(key1, "AES");
                
                //加密
                Cipher cipher=Cipher.getInstance("AES/ECB/PKCS5padding");
                cipher.init(Cipher.ENCRYPT_MODE, key2);
                byte[] result = cipher.doFinal(src.getBytes());
                System.out.println("jdkAES加密: "+Hex.encodeHexString(result));  //转换为十六进制
                
                //解密
                cipher.init(Cipher.DECRYPT_MODE, key2);
                result = cipher.doFinal(result);
                System.out.println("jdkAES解密: "+new String(result));  //转换字符串
            } catch (Exception e) {
        
                e.printStackTrace();
            }
        }

bc的实现（同样使用了添加provider的做法）：

public static void bcAES(){
        
            try {
        
                Security.addProvider(new BouncyCastleProvider());
                
                //生成key
                KeyGenerator keyGenerator=KeyGenerator.getInstance("AES", "BC");
                keyGenerator.getProvider();
                keyGenerator.init(128);      //显示指定密钥长度
                SecretKey secretKey = keyGenerator.generateKey();
                byte[] key1 = secretKey.getEncoded();
                
                //key转换为密钥
                Key key2 = new SecretKeySpec(key1, "AES");
                
                //加密
                Cipher cipher=Cipher.getInstance("AES/ECB/PKCS5padding");
                cipher.init(Cipher.ENCRYPT_MODE, key2);
                byte[] result = cipher.doFinal(src.getBytes());
                System.out.println("jdkAES加密: "+Hex.encodeHexString(result));  //转换为十六进制
                
                //解密
                cipher.init(Cipher.DECRYPT_MODE, key2);
                result = cipher.doFinal(result);
                System.out.println("jdkAES解密: "+new String(result));  //转换字符串
            } catch (Exception e) {
        
                e.printStackTrace();
            }
        }

###### PBE： ######

基于口令的对称加密算法（它其实是对之前的算法的包装，比如说MD5和DES，我这里就是的是对MD5和DES包装的PBE算法，还有其他类型的PBE），口令就是我们俗话说的密码，PBE中有一个salt（盐）的概念，盐就是干扰码

加密的数据：

private static String src="Hello PBE";

导入的类：

import java.security.Key;
    import java.security.SecureRandom;
    
    import javax.crypto.Cipher;
    import javax.crypto.SecretKeyFactory;
    import javax.crypto.spec.PBEKeySpec;
    import javax.crypto.spec.PBEParameterSpec;
    import org.apache.commons.codec.binary.Base64;

JDk的实现：

public static void jdkPBE(){
        
            try {
        
                //初始化盐
                SecureRandom random=new SecureRandom();
                byte[] salt = random.generateSeed(8);   //指定为8位的盐 （盐就是干扰码，通过添加干扰码增加安全）
                
                //口令和密钥
                String password="lynu";              //口令
                PBEKeySpec pbeKeySpec=new PBEKeySpec(password.toCharArray());
                SecretKeyFactory factory=SecretKeyFactory.getInstance("PBEWITHMD5andDES");
                Key key=factory.generateSecret(pbeKeySpec);  //密钥
                
                //加密
                PBEParameterSpec pbeParameterSpec=new PBEParameterSpec(salt, 100);   //参数规范，第一个参数是盐，第二个是迭代次数（经过散列函数多次迭代）
                Cipher cipher=Cipher.getInstance("PBEWITHMD5andDES");
                cipher.init(Cipher.ENCRYPT_MODE, key,pbeParameterSpec);
                byte[] result = cipher.doFinal(src.getBytes());
                System.out.println("jdk PBE加密: "+Base64.encodeBase64String(result));
                
                
                //解密
                cipher.init(Cipher.DECRYPT_MODE, key,pbeParameterSpec);
                result = cipher.doFinal(result);
                System.out.println("jdk PBE解密: "+new String(result));
                
            } catch (Exception e) {
        
                e.printStackTrace();
            }
            
        }

###### 非对称的算法： ######

非对称算法就是发送方和接收方的密钥是不一样的，非对称相对于对称来说，有公钥和私钥的概念，基本上公钥是公开的，比如会在网络上传输，而私钥安全性要求就要高很多了，因为私钥是要保密的

基本的非对称算法有DH，RSA，ELGamal算法

###### DH： ######

基于交换交换的非对称算法，接收方需要得到接收方的key构建本地密钥，而接收方也需要得到发送方的key构建自己本地的密钥。只有JDK的实现  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly92dmNhdC5ibG9nLmNzZG4ubmV0_size_16_color_FFFFFF_t_70 5]  
需要加密的数据：

private static String src="Hello DH";

需要导入的类：

import java.security.KeyFactory;
    import java.security.KeyPair;
    import java.security.KeyPairGenerator;
    import java.security.PrivateKey;
    import java.security.PublicKey;
    import java.security.spec.X509EncodedKeySpec;
    import java.util.Objects;
    import javax.crypto.Cipher;
    import javax.crypto.KeyAgreement;
    import javax.crypto.SecretKey;
    import javax.crypto.interfaces.DHPublicKey;
    import javax.crypto.spec.DHParameterSpec;

JDK的实现：

public static void jdkDH(){
        
            try {
        
                //初始化发送方密钥
                KeyPairGenerator senderKeyPairGenerator=KeyPairGenerator.getInstance("DH");
                senderKeyPairGenerator.initialize(512);   //密钥长度
                KeyPair senderKeyPair = senderKeyPairGenerator.generateKeyPair();
                byte[] senderPublicKeyEnc = senderKeyPair.getPublic().getEncoded();  //发送方key,需传递给接收方（网络，文件）
                
                //初始化接收方密钥
                KeyFactory factory=KeyFactory.getInstance("DH");
                X509EncodedKeySpec x509EncodedKeySpec=new X509EncodedKeySpec(senderPublicKeyEnc);  //根据从发送方得到的key解析
                PublicKey receiverPublicKey=factory.generatePublic(x509EncodedKeySpec);
                DHParameterSpec dhParameterSpec=((DHPublicKey)receiverPublicKey).getParams();
                KeyPairGenerator receiverKeyPairGenerator=KeyPairGenerator.getInstance("DH");
                receiverKeyPairGenerator.initialize(dhParameterSpec);
                KeyPair receiverKeyPair = receiverKeyPairGenerator.generateKeyPair();
                PrivateKey receiverPrivateKey = receiverKeyPair.getPrivate();
                byte[] receiverPublicKeyEnc = receiverKeyPair.getPublic().getEncoded();
                
                //密钥构建
                KeyAgreement receiverKeyAgreement=KeyAgreement.getInstance("DH");
                receiverKeyAgreement.init(receiverPrivateKey);
                receiverKeyAgreement.doPhase(receiverPublicKey, true);
                SecretKey receiverDESKey=receiverKeyAgreement.generateSecret("DES");  //发送发密钥(公钥)
                KeyFactory senderKeyFactory=KeyFactory.getInstance("DH");
                x509EncodedKeySpec=new X509EncodedKeySpec(receiverPublicKeyEnc);
                PublicKey senderPublicKey=senderKeyFactory.generatePublic(x509EncodedKeySpec);
                KeyAgreement senderKeyAgreement=KeyAgreement.getInstance("DH");
                senderKeyAgreement.init(senderKeyPair.getPrivate());
                senderKeyAgreement.doPhase(senderPublicKey, true);
                SecretKey senderDESKey=senderKeyAgreement.generateSecret("DES");        //接收方密钥(私钥)
                if(Objects.equals(receiverDESKey, senderDESKey)){
        
                    System.out.println("双方密钥相同");
                }
                //加密
                Cipher cipher=Cipher.getInstance("DES");
                cipher.init(Cipher.ENCRYPT_MODE, senderDESKey);
                byte[] result = cipher.doFinal(src.getBytes());
                System.out.println("jdk DH加密: "+org.apache.commons.codec.binary.Base64.encodeBase64String(result));
                
                //解密            
                cipher.init(Cipher.DECRYPT_MODE, receiverDESKey);
                result=cipher.doFinal(result);
                System.out.println("jdk DH解密: "+new String(result));
            } catch (Exception e) {
        
                e.printStackTrace();
            }
    
        }

###### RSA： ######

RSA相较于DH算法的实现简单，适用范围较广，公钥和私钥的创建较简单，而且支持公钥加密，私钥解密或者是私钥加密，公钥解密两种方式

要加密的数据：

private static String src="Hello RSA";

要导入的类：

import java.security.KeyFactory;
    import java.security.KeyPair;
    import java.security.KeyPairGenerator;
    import java.security.PrivateKey;
    import java.security.PublicKey;
    import java.security.interfaces.RSAPrivateKey;
    import java.security.interfaces.RSAPublicKey;
    import java.security.spec.PKCS8EncodedKeySpec;
    import java.security.spec.X509EncodedKeySpec;
    import javax.crypto.Cipher;
    import org.apache.commons.codec.binary.Base64;

JDK的实现，公钥加密，私钥解密和私钥加密，公钥解密两种方式：

public static void jdkRSA(){
        
            try {
        
                KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
                keyPairGenerator.initialize(512);
                KeyPair keyPair = keyPairGenerator.generateKeyPair();
                RSAPublicKey rsaPublicKey=(RSAPublicKey) keyPair.getPublic();           //公钥
                RSAPrivateKey rsaPrivateKey=(RSAPrivateKey) keyPair.getPrivate();       //私钥
                System.out.println("public key:"+Base64.encodeBase64String(rsaPublicKey.getEncoded()));
                System.out.println("private key:"+Base64.encodeBase64String(rsaPrivateKey.getEncoded()));
                
                //私钥加密，公钥解密--加密
                PKCS8EncodedKeySpec pkcs8EncodedKeySpec=new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
                KeyFactory keyFactory=KeyFactory.getInstance("RSA");
                PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
                Cipher cipher=Cipher.getInstance("RSA");
                cipher.init(Cipher.ENCRYPT_MODE, privateKey);
                byte[] result = cipher.doFinal(src.getBytes());
                System.out.println("RSA私钥加密，公钥解密--加密:"+Base64.encodeBase64String(result));
                
                //私钥加密，公钥解密--解密
                X509EncodedKeySpec x509EncodedKeySpec=new X509EncodedKeySpec(rsaPublicKey.getEncoded());
                keyFactory=KeyFactory.getInstance("RSA");
                PublicKey publicKey=keyFactory.generatePublic(x509EncodedKeySpec);
                cipher=Cipher.getInstance("RSA");
                cipher.init(Cipher.DECRYPT_MODE,publicKey);
                result = cipher.doFinal(result);
                System.out.println("RSA私钥加密，公钥解密--解密:"+new String(result));
                
                //公钥加密，私钥解密--加密
                x509EncodedKeySpec=new X509EncodedKeySpec(rsaPublicKey.getEncoded());
                keyFactory=KeyFactory.getInstance("RSA");
                publicKey=keyFactory.generatePublic(x509EncodedKeySpec);
                cipher=Cipher.getInstance("RSA");
                cipher.init(Cipher.ENCRYPT_MODE,publicKey);
                result = cipher.doFinal(src.getBytes());
                System.out.println("RSA公钥加密，私钥解密--加密:"+Base64.encodeBase64String(result));
                
                //公钥加密，私钥解密--解密
                pkcs8EncodedKeySpec=new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
                keyFactory=KeyFactory.getInstance("RSA");
                privateKey =keyFactory.generatePrivate(pkcs8EncodedKeySpec);
                cipher=Cipher.getInstance("RSA");
                cipher.init(Cipher.DECRYPT_MODE,privateKey);
                result=cipher.doFinal(result);
                System.out.println("RSA公钥加密，私钥解密--解密:"+new String(result));
                
                
            } catch (Exception e) {
        
                e.printStackTrace();
            }
        }

###### ELGamal： ######

ELGamal算法的和AES一样存在密钥长度的限制，解决方法和AES一致。不过ELGamal只支持公钥加密，私钥解密这种方式。只有bc的实现方式

要加密的数据：

private static String src="Hello ELGamal";

导入的类：

import java.security.AlgorithmParameterGenerator;
    import java.security.AlgorithmParameters;
    import java.security.KeyFactory;
    import java.security.KeyPair;
    import java.security.KeyPairGenerator;
    import java.security.PrivateKey;
    import java.security.PublicKey;
    import java.security.SecureRandom;
    import java.security.Security;
    import java.security.spec.PKCS8EncodedKeySpec;
    import java.security.spec.X509EncodedKeySpec;
    import javax.crypto.Cipher;
    import javax.crypto.spec.DHParameterSpec;
    import org.apache.commons.codec.binary.Base64;
    import org.bouncycastle.jce.provider.BouncyCastleProvider;

bc的实现方式：

public static void bcELGamal(){
        
            try {
        
                //加载provider
                Security.addProvider(new BouncyCastleProvider());
                
                //初始化密钥
                AlgorithmParameterGenerator algorithmParameterGenerator=AlgorithmParameterGenerator.getInstance("ELGamal");
                algorithmParameterGenerator.init(256);
                AlgorithmParameters algorithmParameters=algorithmParameterGenerator.generateParameters();
                DHParameterSpec dhParameterSpec=(DHParameterSpec)algorithmParameters.getParameterSpec(DHParameterSpec.class);
                KeyPairGenerator keyPairGenerator=KeyPairGenerator.getInstance("ELGamal");
                keyPairGenerator.initialize(dhParameterSpec, new SecureRandom());
                KeyPair keyPair=keyPairGenerator.generateKeyPair();
                PublicKey elGamalPublicKey=keyPair.getPublic();        //公钥
                PrivateKey elGamalPrivateKey=keyPair.getPrivate();     //私钥
                System.out.println("public key:"+Base64.encodeBase64String(elGamalPublicKey.getEncoded()));
                System.out.println("private key:"+Base64.encodeBase64String(elGamalPrivateKey.getEncoded()));
                
                //公钥加密，私钥解密--加密
                X509EncodedKeySpec x509EncodedKeySpec=new X509EncodedKeySpec(elGamalPublicKey.getEncoded());
                KeyFactory keyFactory=KeyFactory.getInstance("ELGamal");
                PublicKey publicKey=keyFactory.generatePublic(x509EncodedKeySpec);
                Cipher cipher=Cipher.getInstance("ELGamal");
                cipher.init(Cipher.ENCRYPT_MODE,publicKey);
                byte[] result = cipher.doFinal(src.getBytes());
                System.out.println("ELGamal加密:"+Base64.encodeBase64String(result));
                
                //公钥加密，私钥解密--解密
                PKCS8EncodedKeySpec pkcs8EncodedKeySpec=new PKCS8EncodedKeySpec(elGamalPrivateKey.getEncoded());
                keyFactory=KeyFactory.getInstance("ELGamal");
                PrivateKey privateKey =keyFactory.generatePrivate(pkcs8EncodedKeySpec);
                cipher=Cipher.getInstance("ELGamal");
                cipher.init(Cipher.DECRYPT_MODE,privateKey);
                result=cipher.doFinal(result);
                System.out.println("ElGamal解密:"+new String(result));
                
            } catch (Exception e) {
        
                e.printStackTrace();
            }
            
        }

> 作者：OverZeal  
> 出处：https://www.cnblogs.com/lz2017/p/6917049.html  
> 本站使用「署名 4.0 国际」创作共享协议，转载请在文章明显位置注明作者及出处。

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