java 实现加密

加密有单向加密和双向加密之分,也叫对称加密和非对称加密,双向加密就是把数据加密后,还可以解密成原来的数据,但是需要使用到密钥,而且必须是同一个密钥.才可以解密成原来的数据.一开始我也不知道,密钥是使用系统生成的密钥,加密和解密分开操作的时候,加密过后,数据就解密不出来了.java实现加密的方法有DES,AES,等这些对称加密.单向加密从严格的意义来讲不算加密.只是实现了一定的算法,但是不可以逆转.MD5加密就是一个单向非对称加密的技术.直接上代码

package com.chen;

import java.security.InvalidKeyException;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;

public class Chen {
    // 密钥生成器
    private KeyGenerator kg = null;
    // 密钥
    private SecretKey key = null;
    // 进行加密和解密
    private Cipher cip = null;
    public Chen() throws Exception{
        kg = KeyGenerator.getInstance("DES");
        key = kg.generateKey();
        cip = Cipher.getInstance("DES");
    }
    public byte[] encrypt(byte[] s) throws InvalidKeyException, IllegalBlockSizeException, BadPaddingException{
        // 初始化
        cip.init(Cipher.ENCRYPT_MODE, key);
        // 加密
        return cip.doFinal(s);
    }
    public byte[] decrypt(byte[] b) throws InvalidKeyException, IllegalBlockSizeException, BadPaddingException{
        // 初始化
        cip.init(Cipher.DECRYPT_MODE, key);
        // 解密
        return cip.doFinal(b);
    }
    public static void main(String[] args) {
        try {
            Chen chen = new Chen();
            String str = "aba萨芬斯蒂芬";
            // 加密
            byte[] temp = chen.encrypt(str.getBytes());
            // 解密
            byte[] flag = chen.decrypt(temp);
            System.out.println("明文 : " + str);
            System.out.println("加密后的数据 : " + new String(temp));
            System.out.println("解密后的数据 : " + new String(flag));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

AES加密和解密的代码

package crypt;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

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 AEScrypt {

    //  key生成器
    private KeyGenerator kg;
    // 密钥
    private SecretKey key;
    // 加密解密类
    private Cipher cipher;
    public AEScrypt() throws NoSuchAlgorithmException, NoSuchPaddingException{
        kg = KeyGenerator.getInstance("AES");
        System.out.println(kg.getProvider().getName());
        key = kg.generateKey();
        cipher = Cipher.getInstance("AES");
        System.out.println(cipher.getProvider());
    }
    public byte[] encrypt(byte[] b) throws InvalidKeyException, IllegalBlockSizeException, BadPaddingException{
        // 初始化
        cipher.init(Cipher.ENCRYPT_MODE, key);
        return cipher.doFinal(b);
    }
    public byte[] decrypt(byte[] b) throws InvalidKeyException, IllegalBlockSizeException, BadPaddingException{
        // 初始化
        cipher.init(Cipher.DECRYPT_MODE, key);
        // 解密
        return cipher.doFinal(b);

    }
    public static void main(String[] args) {
        try {
            AEScrypt aes = new AEScrypt();
            String s = "safasf的送饭饭2342(&((*";
            byte[] temp = aes.encrypt(s.getBytes());
            byte[] flag = aes.decrypt(temp);
            System.out.println("明文 : " + s);
            System.out.println("加密 : " + new String(temp));
            System.out.println("解密 : " + new String(flag));
        } catch (Exception e) {

            e.printStackTrace();
        }

    }
}

非对称RSA,有连个密钥,一个公开密钥,一个私有密钥,通过其中一个密钥加密,在通过其他一个密钥解密

package crypt;
import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;  

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

public class RSAcrypt {  

    /**
     * 加密
     * @param publicKey
     * @param srcBytes
     * @return
     * @throws NoSuchAlgorithmException
     * @throws NoSuchPaddingException
     * @throws InvalidKeyException
     * @throws IllegalBlockSizeException
     * @throws BadPaddingException
     */
    protected byte[] encrypt(RSAPublicKey publicKey,byte[] srcBytes) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException{
        if(publicKey!=null){
            //Cipher负责完成加密或解密工作，基于RSA
            Cipher cipher = Cipher.getInstance("RSA");
            //根据公钥，对Cipher对象进行初始化
            cipher.init(Cipher.ENCRYPT_MODE, publicKey);
            byte[] resultBytes = cipher.doFinal(srcBytes);
            return resultBytes;
        }
        return null;
    }  

    /**
     * 解密
     * @param privateKey
     * @param srcBytes
     * @return
     * @throws NoSuchAlgorithmException
     * @throws NoSuchPaddingException
     * @throws InvalidKeyException
     * @throws IllegalBlockSizeException
     * @throws BadPaddingException
     */
    protected byte[] decrypt(RSAPrivateKey privateKey,byte[] srcBytes) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException{
        if(privateKey!=null){
            //Cipher负责完成加密或解密工作，基于RSA
            Cipher cipher = Cipher.getInstance("RSA");
            //根据公钥，对Cipher对象进行初始化
            cipher.init(Cipher.DECRYPT_MODE, privateKey);
            byte[] resultBytes = cipher.doFinal(srcBytes);
            return resultBytes;
        }
        return null;
    }  

    /**
     * @param args
     * @throws NoSuchAlgorithmException
     * @throws BadPaddingException
     * @throws IllegalBlockSizeException
     * @throws NoSuchPaddingException
     * @throws InvalidKeyException
     */
    public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException {
        RSAcrypt rsa = new RSAcrypt();
        String msg = "郭XX-精品相声";
        //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1024位
        keyPairGen.initialize(1024);
        //生成一个密钥对，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        //得到私钥
        RSAPrivateKey privateKey = (RSAPrivateKey)keyPair.getPrivate();
        //得到公钥
        RSAPublicKey publicKey = (RSAPublicKey)keyPair.getPublic();  

        //用公钥加密
        byte[] srcBytes = msg.getBytes();
        byte[] resultBytes = rsa.encrypt(publicKey, srcBytes);  

        //用私钥解密
        byte[] decBytes = rsa.decrypt(privateKey, resultBytes);  

        System.out.println("明文是:" + msg);
        System.out.println("加密后是:" + new String(resultBytes));
        System.out.println("解密后是:" + new String(decBytes));
    }  

}