[网络协议]https中对称算法AES 摘要算法SHA1 SHA256 不对称RSA java实现

import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.util.Base64;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
public class Keypair {
	public static void main(String[] args) {
		String s="121313qwqee";
		try {
			KeyPairGenerator kpg=KeyPairGenerator.getInstance("RSA");
			KeyPair kp=kpg.generateKeyPair();
			kpg.initialize(1024);
			PrivateKey pri=kp.getPrivate();               //生成私钥
			PublicKey pub=kp.getPublic();                 //生成公钥
			                     
	//---------------------------------------------------------------------		
			try {
					Cipher cipher=Cipher.getInstance("RSA");   //静态方法生成实例
					cipher.init(Cipher.PUBLIC_KEY,pub);       //实例初始化
					byte[] enout=cipher.doFinal(s.getBytes()); //文本加密
					
	//--------------------------------------------------------------------
					cipher.init(Cipher.PRIVATE_KEY,pri);       //实例初始化
					byte[] deout=cipher.doFinal(enout);         //解密
				
			    	for(byte k:deout) {
						System.out.print((char)k);             //121313qwqee
					}
					
	//-----------------------------------------------------------------------				
				} catch (InvalidKeyException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (NoSuchPaddingException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (IllegalBlockSizeException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (BadPaddingException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}

		
		} catch (NoSuchAlgorithmException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
			
	}         
		
	
}

?JDK文档的标准使用步骤：

Cipher cipher=Cipher.getInstance("算法“）:

GCMParameterSpec? ? s.....? ? ? ? 我理解s就是密钥

? ? ? ? cipher.init(mode,s)? ? ? ? ? mode为加解密模式

? ? ? ? cipher.updateAADC...

? ? ? ? cipher.update......

? ? ? ?cipher.doFinal(被加解密文本）? ?必须是 byte[]

此程序经验证，只能公钥加密，私钥解密，或者私钥加密，公钥解密。

Cipher cipher=Cipher.getInstance("RSA"); ? //静态方法生成实例
?? ??? ??? ??? ??? ?cipher.init(Cipher.PUBLIC_KEY,pri); ? ? ? //实例初始化
?? ??? ??? ??? ??? ?byte[] enout=cipher.doFinal(s.getBytes()); //文本加密
?? ??? ??? ? ? ? ? ? cipher.init(Cipher.PRIVATE_KEY,pub); ? ? ? //实例初始化

以上几句是用私钥加密，公钥解密。

Cipher.PUBLIC_KEY? ?：加密模式? ? ? ? ? ? ? ? ? ? ? Cipher.PRIVATE_KEY? ：解密模式

打开byte[] enout? ?是一堆乱码，证明已加密。

生成的公钥私钥为文本形式的十六进制（去除了0x）表示的一长串数字。它没有使用byte 数组，就不用Base64 转码了。我们可以把它作为字符串用FileOutputStream 把它读写入存为文件。现在我们可以用RSA编写自己的加解密程序了。首先生成密钥对，对想保护的文件用私密加密，把公钥存入U盘，解密时调入公钥解密。

import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.util.Base64;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
public class Keypair {
	public static void main(String[] args) {
		
		String s="121313qwqee";
		try {
			MessageDigest md=MessageDigest.getInstance("SHA-256");     //静态方法生成实例
			md.update(s.getBytes());                                  //初始化
			//MessageDigest tc1= md.clone();
			byte[] tomd=md.digest();     //计算  问题现在输出的是byte数字，大于127就是负数，如用Base64转换，也是把负数转化，必须把大于127的数转换为正数，很简单，加256就可以了
			String sout="";
			int z;
			for(int n=0;n<tomd.length;n++) {
				if((z=tomd[n])<0) {               //大于127的数加256
					z=z+256;
				}
				sout=sout+Integer.toHexString(z);   //转为字符串形式
			}
			System.out.println(sout);              //cf69dee551eb3ec14e1522bfc5d8de70538c9e640154e62781f838967e73
		} catch (NoSuchAlgorithmException e2) {
			// TODO Auto-generated catch block
			e2.printStackTrace();
		}
			
		System.out.println();
	//------------------------------------------------------------------------	
		try {
			KeyPairGenerator kpg=KeyPairGenerator.getInstance("RSA");
			KeyPair kp=kpg.generateKeyPair();
			kpg.initialize(1024);
			PrivateKey pri=kp.getPrivate();               //生成私钥
			PublicKey pub=kp.getPublic();                 //生成公钥
		//---------------------------------------------------------------
		    KeyGenerator kg=KeyGenerator.getInstance("AES");
		    kg.init(128);
		    SecretKey key=kg.generateKey();                 //生成对称用密钥
		//-------------------------------------------------    
		    try {
				Cipher cipher3=Cipher.getInstance("AES");
				cipher3.init(Cipher.ENCRYPT_MODE, key);
				byte[] denout=cipher3.doFinal(s.getBytes()); //对称加密
		//-------------------------------------------------------		
				cipher3.init(Cipher.DECRYPT_MODE, key);
				byte[] ddeout=cipher3.doFinal(denout);        //对称解密
				for(byte z:ddeout) {
					System.out.print((char)z);
				
				}
				System.out.println();
			//----------------------------------------------------	
			} catch (InvalidKeyException e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
			} catch (NoSuchPaddingException e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
			} catch (IllegalBlockSizeException e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
			} catch (BadPaddingException e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
			}
		    
	//---------------------------------------------------------------------		
			try {
					Cipher cipher=Cipher.getInstance("RSA");   //静态方法生成实例
					cipher.init(Cipher.PUBLIC_KEY,pri);       //实例初始化
					byte[] enout=cipher.doFinal(s.getBytes()); //文本加密
			
	//--------------------------------------------------------------------
					cipher.init(Cipher.PRIVATE_KEY,pub);       //实例初始化
					byte[] deout=cipher.doFinal(enout);         //解密
				
			    	for(byte k:deout) {
						System.out.print((char)k);             //121313qwqee
					}
					
	//-----------------------------------------------------------------------				
				} catch (InvalidKeyException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (NoSuchPaddingException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (IllegalBlockSizeException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (BadPaddingException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}

		
		} catch (NoSuchAlgorithmException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
			
	}         
		
	
}