【java】加密解密的规则。示例

在实际业务中，可能会对离线的文本内容进行加密和解密，这里展示一套加密解密的规则：

要求，不管是加密还是解密，都必须有SessionKey

加密方法：
1.    对会话密钥sessionKey进行MD5处理；
2.    取MD5值前8位作为密钥，对数据进行DES加密。DES加密的Java代码参考：        Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");  
    DESKeySpec desKeySpec = new DESKeySpec(key.getBytes("UTF-8"));  
    SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");  
    // 密钥
    SecretKey secretKey = keyFactory.generateSecret(desKeySpec);  
    // 偏移量
    IvParameterSpec iv = new IvParameterSpec(key.getBytes("UTF-8"));  
    cipher.init(Cipher.ENCRYPT_MODE, secretKey, iv);  
    byte[] retBytes = cipher.doFinal(message.getBytes("UTF-8"));  
    return Base64.encode(retBytes);
解密方法：
1.    对会话密钥sessionKey进行MD5处理；
2.    取MD5值前8位作为密钥，对数据进行DES解密。DES解密的Java代码参考：        Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");  
    DESKeySpec desKeySpec = new DESKeySpec(key.getBytes("UTF-8"));  
    SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");  
    // 密钥
    SecretKey secretKey = keyFactory.generateSecret(desKeySpec);  
    // 偏移量
    IvParameterSpec iv = new IvParameterSpec(key.getBytes("UTF-8"));  
    cipher.init(Cipher.DECRYPT_MODE, secretKey, iv);  
    byte[] retBytes = cipher.doFinal(Base64.decode(message));  
　　return new String(retBytes, "UTF-8");

代码展示：

import org.apache.ws.commons.util.Base64;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
import javax.crypto.spec.IvParameterSpec;

pom.xml文件引入Jar

　　　　<dependency>
          <groupId>org.apache.ws.commons.util</groupId>
          <artifactId>ws-commons-util</artifactId>
          <version>1.0.2</version>
      </dependency>

/**
     * 加密  方法
         * 这里暂时把sessionkey 写死
     * @param context 要加密的正文内容
     * @return
     */
private String  encrypt(String context){
        String SESSIONKEY = "test";
        StringBuffer buffer = new StringBuffer();
        try {
            String getMD5Code = MD5Util.GetMD5Code(SESSIONKEY);
            String sessionKey = getMD5Code.substring(0, 8);

            Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
            DESKeySpec desKeySpec = new DESKeySpec(sessionKey.getBytes("UTF-8"));
            SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
            // 密钥
            SecretKey secretKey = keyFactory.generateSecret(desKeySpec);
            // 偏移量
            IvParameterSpec iv = new IvParameterSpec(sessionKey.getBytes("UTF-8"));
            cipher.init(Cipher.ENCRYPT_MODE, secretKey, iv);

            String [] messageArr = context.split(IBills.FILE_CONTENT_SPLIT_MARK);
            for (String s : messageArr) {
                byte[] retBytes = cipher.doFinal(s.getBytes("UTF-8"));
                buffer.append(Base64.encode(retBytes)+IBills.FILE_CONTENT_SPLIT_MARK);
            }

        }catch (Exception e){
            throw new LunaException("加密失败", LunaResultBean.ERROR_BUSINESS);
        }

        return buffer.toString();
    }

/**
     * 解密 上传文件内容
     * 这里先将sessionkey写死 值为test
     * @param context 要解密的文本内容
     * @return
     */
    private String decrypt(String context){

        String SESSIONKEY = "test";
        StringBuffer buffer = new StringBuffer();
        try {
            String getMD5Code = MD5Util.GetMD5Code(SESSIONKEY);
            String sessionKey = getMD5Code.substring(0, 8);

            Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
            DESKeySpec desKeySpec = new DESKeySpec(sessionKey.getBytes("UTF-8"));
            SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
            // 密钥
            SecretKey secretKey = keyFactory.generateSecret(desKeySpec);
            // 偏移量
            IvParameterSpec iv = new IvParameterSpec(sessionKey.getBytes("UTF-8"));
            cipher.init(Cipher.DECRYPT_MODE, secretKey, iv);
            String [] messageArr = context.split(FILE_CONTENT_SPLIT_MARK);
            for (String s : messageArr) {
                byte[] retBytes = cipher.doFinal(Base64.decode(s));
                buffer.append(new String(retBytes, "UTF-8")+FILE_CONTENT_SPLIT_MARK);
            }

        }catch (Exception e){
            throw new LunaException("解密失败", LunaResultBean.ERROR_BUSINESS);
        }

        return buffer.toString();
    }

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