对称加密算法

1、对称加密：采用单钥对信息进行加密和解密，即同一个秘钥既可以对信息进行加密，也可以进行解密。此类型称之为对称加密。特点速度快，常用于对大量数据信息或文件加密时使用。常用例子：DES、IDEA、RC2、RC4、SKIPJACK、RC5、AES。

优点：速度快，对称性加密通常在消息发送方需要加密大量数据时使用，算法公开、计算量小、加密速度快、加密效率高。

缺点：在数据传送前，发送方和接收方必须商定好秘钥，然后使双方都能保存好秘钥。其次如果一方的秘钥被泄露，那么加密信息也就不安全了。另外，每对用户每次使用对称加密算法时，都需要使用其他人不知道的唯一秘钥，这会使得收、发双方所拥有的钥匙数量巨大，密钥管理成为双方的负担

AES：密钥的长度可以为128、192和256位，也就是16个字节、24个字节和32个字节

DES：密钥的长度64位，8个字节。

1.AES加密算法

package com.yirong;

import java.security.Key;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

import com.sun.org.apache.xerces.internal.impl.dv.util.Base64;

public class Test_AES {

	//加密的内容
	private static String src = "security AES";	
	
	public static void main(String[] args) {

		jdkAES();
	}

	public static void jdkAES() {
		
		try {
			//创建AES的Key生产者
			KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
			// 利用用户密码作为随机数初始化出
			keyGenerator.init(new SecureRandom());
			// 根据用户密码，生成一个密钥
			SecretKey secretKey = keyGenerator.generateKey();
			// 返回基本编码格式的密钥，如果此密钥不支持编码，则返回null
			byte[] keyBytes = secretKey.getEncoded();
			
			// 转换为AES专用密钥
			Key key = new SecretKeySpec(keyBytes, "AES");
			
			
			// 创建密码器
			Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
			// 初始化为加密模式的密码器
			cipher.init(Cipher.ENCRYPT_MODE, key);
			//加密
			byte[] result = cipher.doFinal(src.getBytes());
			System.out.println("jdk aes encrypt:" + Base64.encode(result));
			
			// 初始化为解密模式的密码器
			cipher.init(Cipher.DECRYPT_MODE, key);
			//解密
			result = cipher.doFinal(result);
			System.out.println("jdk aes encrypt:" + new String(result));
			
			
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
}

2.DES加密算法

package com.yirong;

import java.security.Key;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
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.DESKeySpec;
import javax.crypto.spec.DESedeKeySpec;

import org.apache.commons.codec.binary.Hex;

public class Test_DES {

	//加密的内容
	private static String src = "security sha";
	
	public static void main(String[] args) {

		jdk3DES();
		jdkDES();
	}
	
	public static void jdkDES() {

		try {
			//生成一个key
			KeyGenerator keyGenerator;
			keyGenerator = KeyGenerator.getInstance("DES");
			keyGenerator.init(56);
			SecretKey secretKey = keyGenerator.generateKey();
			//得到key数组
			byte[] bytesKey = secretKey.getEncoded();
			
			//key转换
			DESKeySpec desKeySpec = new DESKeySpec(bytesKey);
			//加密方式
			SecretKeyFactory factory = SecretKeyFactory.getInstance("DES");
			//生成的秘钥
			Key secret = factory.generateSecret(desKeySpec);
			
			//加密   加解密算法，工作模式，填充方式
			Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
			cipher.init(Cipher.ENCRYPT_MODE, secret);
			byte[] result = cipher.doFinal(src.getBytes());
			System.out.println("jdk des encrypt: " + Hex.encodeHexString(result));
			
			//解密
			cipher.init(Cipher.DECRYPT_MODE, secret);
			result = cipher.doFinal(result);
			System.out.println("jdk des encrypt: " + new String(result));
			
			
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}
	
	
	public static void jdk3DES() {
		
		try {
			//生成一个key
			KeyGenerator keyGenerator;
			keyGenerator = KeyGenerator.getInstance("DESede");
			//生成的长度
			//keyGenerator.init(128);
			keyGenerator.init(new SecureRandom());
			
			SecretKey secretKey = keyGenerator.generateKey();
			//得到key数组
			byte[] bytesKey = secretKey.getEncoded();
			
			//key转换
			DESedeKeySpec desKeySpec = new DESedeKeySpec(bytesKey);
			//加密方式
			SecretKeyFactory factory = SecretKeyFactory.getInstance("DESede");
			//生成的秘钥
			Key secret = factory.generateSecret(desKeySpec);
			
			//加密   加解密算法，工作模式，填充方式
			Cipher cipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
			cipher.init(Cipher.ENCRYPT_MODE, secret);
			byte[] result = cipher.doFinal(src.getBytes());
			System.out.println("jdk des encrypt: " + Hex.encodeHexString(result));
			
			//解密
			cipher.init(Cipher.DECRYPT_MODE, secret);
			result = cipher.doFinal(result);
			System.out.println("jdk des encrypt: " + new String(result));
			
			
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

3.PBE加密算法

package com.yirong;

import java.security.Key;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

import com.sun.org.apache.xerces.internal.impl.dv.util.Base64;

public class Test_PBE {

	public static void main(String[] args) {
		jdkPbe();
	}
	//加密的内容
	private static String src = "security pbe";	
		
	public static void jdkPbe() {
		
		try {
			//初始化盐
			SecureRandom random = new SecureRandom();
			byte[] salt = random.generateSeed(8);
			
			//口令密钥
			String password = "123";
			PBEKeySpec pbeKeySpec = new PBEKeySpec(password.toCharArray());
			SecretKeyFactory factory = SecretKeyFactory.getInstance("PBEWITHMD5andDES");
			Key key = factory.generateSecret(pbeKeySpec);
			
			//加密
			PBEParameterSpec parameterSpec = new PBEParameterSpec(salt, 100);
			Cipher cipher = Cipher.getInstance("PBEWITHMD5andDES");
			cipher.init(Cipher.ENCRYPT_MODE, key,parameterSpec);
			byte[] result = cipher.doFinal(src.getBytes());
			System.out.println("jdk pbe encrypt:" + Base64.encode(result));
			
			//解密
			cipher.init(Cipher.DECRYPT_MODE, key,parameterSpec);
			result = cipher.doFinal(result);
			System.out.println("jdk pde encrypt:" + new String(result));
			
			
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

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