des加密工具类（des加密算法详解）

  des算法简介

des 算法

  des算法为密码*中的对称密码*，又被称为美国数据加密标准，是1972年美国ibm公司研制的对称密码*加密算法。明文按64位进行分组，密钥长64位，密钥事实上是56位参与des运算（第8、16、24、32、40、48、56、64位是校验位，使得每个密钥都有奇数个1）分组后的明文组和56位的密钥按位替代或交换的方法形成密文组的加密方法。

  des算法具有极高安全性，除了用穷举搜索法对des算法进行攻击外，还没有发现更有效的办法。而56位长的密钥的穷举空间为2^56，这意味着如果一台计算机的速度是每一秒钟检测一百万个密钥，则它搜索完全部密钥就需要将近2285年的时间，可见，这是难以实现的。然而，这并不等于说des是不可破解的。而实际上，随着硬件技术和internet的发展，其破解的可能性越来越大，而且，所需要的时间越来越少。使用经过特殊设计的硬件并行处理要几个小时。

  为了克服des密钥空间小的缺陷，人们又提出了三重des的变形方式。

  maven 依赖

  工具类对于加密后使用base64进行编码，所以需要依赖apache commons codec。

<dependency>
    <groupid>commons-codec</groupid>
    <artifactid>commons-codec</artifactid>
    <version>1.9</version>
</dependency>
<dependency>
    <groupid>log4j</groupid>
    <artifactid>log4j</artifactid>
    <version>1.2.17</version>
</dependency>

  工具类实现

  desutil提供了针对文本内容、字节数组内容的加解密实现，desutil工具类可以直接复制使用，代码如下：

package com.arhorchin.securitit.enordecryption.des;
import java.security.key;
import javax.crypto.cipher;
import javax.crypto.secretkeyfactory;
import javax.crypto.spec.deskeyspec;
import javax.crypto.spec.ivparameterspec;
import org.apache.commons.codec.binary.base64;
import org.apache.log4j.logger;
/**
 * @author securitit.
 * @note des加密算法实现.
 */
public class desutil {
    /**
     * logger.
     */
    private static logger logger = logger.getlogger(desutil.class);
    /**
     * 数据编码.
     */
    private static final string charset_utf8 = "utf-8";
    /**
     * 算法编号.
     */
    public static final string des_name = "des";
    /**
     * cbc模式串.
     */
    public static final string des_name_ecb = "des/cbc/pkcs5padding";
    /**
     * 初始向量.
     */
    public static final byte[] des_key_iv = { 1, 2, 3, 4, 5, 6, 7, 8 };
    /**
     * 根据密码生成key.要求：密码长度是8的倍数.
     * @param deskeypwd 密码字符串.
     * @return des密钥.
     * @throws exception 可能异常.
     */
    public static string generatedeskey(string deskeypwd) throws exception {
        deskeyspec deskeyspec = null;
        secretkeyfactory keyfactory = null;
        byte[] keybytes = null;
        deskeyspec = new deskeyspec(deskeypwd.getbytes(charset_utf8));
        keyfactory = secretkeyfactory.getinstance(des_name);
        keybytes = keyfactory.generatesecret(deskeyspec).getencoded();
        return base64.encodebase64string(keybytes);
    }
    /**
     * 对文本内容进行加密.
     * @param plaintext 待加密明文内容.
     * @param deskey des密钥.
     * @return 加密的密文.
     */
    public static string encodetext(string plaintext, string deskey) throws exception {
        byte[] deskeybytes = null;
        byte[] plainbytes = null;
        byte[] cipherbytes = null;
        try {
            deskeybytes = base64.decodebase64(deskey);
            plainbytes = plaintext.getbytes(charset_utf8);
            cipherbytes = encodebycbc(plainbytes, deskeybytes, des_key_iv);
            return base64.encodebase64string(cipherbytes);
        } catch (exception ex) {
            logger.error("desutil.encodetext.", ex);
            return "";
        }
    }
    /**
     * 对文本密文进行解密.
     * @param ciphertext 待解密密文.
     * @param deskey des密钥.
     * @return 解密的明文.
     */
    public static string decodetext(string ciphertext, string deskey) throws exception {
        byte[] deskeybytes = null;
        byte[] cipherbytes = null;
        byte[] plainbytes = null;
        try {
            deskeybytes = base64.decodebase64(deskey);
            cipherbytes = base64.decodebase64(ciphertext);
            plainbytes = decodebycbc(cipherbytes, deskeybytes, des_key_iv);
            return new string(plainbytes, charset_utf8);
        } catch (exception ex) {
            logger.error("desutil.decodetext.", ex);
            return "";
        }
    }
    /**
     * 对字节数组内容进行加密.
     * @param plaintext 待加密明文内容.
     * @param dsekey des密钥.
     * @return 加密的密文.
     */
    public static byte[] encodebytes(byte[] plainbytes, string deskey) throws exception {
        byte[] deskeybytes = null;
        byte[] cipherbytes = null;
        try {
            deskeybytes = base64.decodebase64(deskey);
            cipherbytes = encodebycbc(plainbytes, deskeybytes, des_key_iv);
            return cipherbytes;
        } catch (exception ex) {
            logger.error("desutil.encodebytes.", ex);
            return new byte[0];
        }
    }
    /**
     * 对字节数组密文进行解密.
     * @param ciphertext 待解密密文.
     * @param deskey des密钥.
     * @return 解密的明文.
     */
    public static byte[] decodebytes(byte[] cipherbytes, string deskey) throws exception {
        byte[] deskeybytes = null;
        byte[] plainbytes = null;
        try {
            deskeybytes = base64.decodebase64(deskey);
            plainbytes = decodebycbc(cipherbytes, deskeybytes, des_key_iv);
            return plainbytes;
        } catch (exception ex) {
            logger.error("desutil.decodebytes.", ex);
            return new byte[0];
        }
    }
    /**
     * des算法使用cbc模式进行加密.
     * @param plainbytes 原文内容.
     * @param deskey des密钥.
     * @param keyiv des初始向量.
     * @return 加密后的内容.
     * @throws exception .
     */
    public static byte[] encodebycbc(byte[] plainbytes, byte[] deskey, byte[] keyiv) throws exception {
        key deskey = null;
        deskeyspec desspec = null;
        secretkeyfactory keyfactory = null;
        cipher cipher = null;
        ivparameterspec ivspec = null;
        byte[] cipherout = null;
        desspec = new deskeyspec(deskey);
        keyfactory = secretkeyfactory.getinstance(des_name);
        deskey = keyfactory.generatesecret(desspec);
        cipher = cipher.getinstance(des_name_ecb);
        ivspec = new ivparameterspec(keyiv);
        cipher.init(cipher.encrypt_mode, deskey, ivspec);
        cipherout = cipher.dofinal(plainbytes);
        return cipherout;
    }
    /**
     * des算法使用cbc模式进行解密.
     * @param plainbytes 密文内容.
     * @param deskey des密钥.
     * @param keyiv des初始向量.
     * @return 解密后的内容.
     * @throws exception .
     */
    public static byte[] decodebycbc(byte[] plainbytes, byte[] deskey, byte[] keyiv) throws exception {
        key deskey = null;
        deskeyspec desspec = null;
        secretkeyfactory keyfactory = null;
        cipher cipher = null;
        ivparameterspec ivspec = null;
        byte[] cipherout = null;
        desspec = new deskeyspec(deskey);
        keyfactory = secretkeyfactory.getinstance(des_name);
        deskey = keyfactory.generatesecret(desspec);
        cipher = cipher.getinstance(des_name_ecb);
        ivspec = new ivparameterspec(keyiv);
        cipher.init(cipher.decrypt_mode, deskey, ivspec);
        cipherout = cipher.dofinal(plainbytes);
        return cipherout;
    }
}

  工具类测试

package com.arhorchin.securitit.enordecryption.des;
import java.util.arrays;
/**
 * @author securitit.
 * @note desutil测试类.
 */
public class desutiltester {
    public static void main(string[] args) throws exception {
        string deskeypwd = "1234567887654321";
        string deskey = null;
        string plaintext = "this is 一段明文内容！";
        string ciphertext = null;
        system.out.println("----------------------- 获取des秘钥 -------------------------");
        deskey = desutil.generatedeskey(deskeypwd);
        system.out.println("秘钥：" + deskey);
        system.out.println();
        // 文本加解密测试.
        system.out.println("----------------------- 文本加解密测试 -------------------------");
        system.out.println("明文：" + plaintext);
        ciphertext = desutil.encodetext(plaintext, deskey);
        system.out.println("密文：" + ciphertext);
        plaintext = desutil.decodetext(ciphertext, deskey);
        system.out.println("解密明文：" + plaintext);
        system.out.println();
        system.out.println("----------------------- 字节数组加解密测试 -------------------------");
        byte[] plainbytes = plaintext.getbytes("utf-8");
        byte[] cipherbytes = null;
        system.out.println("明文：" + arrays.tostring(plainbytes));
        cipherbytes = desutil.encodebytes(plainbytes, deskey);
        system.out.println("密文：" + arrays.tostring(cipherbytes));
        plainbytes = desutil.decodebytes(cipherbytes, deskey);
        system.out.println("解密明文：" + arrays.tostring(plainbytes));
        system.out.println();
    }
}

  控制台输出

  查看console中的控制台内容，明文和解密后明文对比，可以确认desutil可以正常工作，控制台如下图：

----------------------- 获取des秘钥 -------------------------
秘钥：mtiyndq3nzg=
----------------------- 文本加解密测试 -------------------------
明文：this is 一段明文内容！
密文：2guhziwpad0klmjyrzerlw83acn0am0f19nz18nf214=
解密明文：this is 一段明文内容！
----------------------- 字节数组加解密测试 -------------------------
明文：[84, 104, 105, 115, 32, 105, 115, 32, -28, -72, -128, -26, -82, -75, -26, -104, -114, -26, -106, -121, -27, -122, -123, -27, -82, -71, -17, -68, -127]
密文：[-38, 11, -121, -52, -123, -87, 105, -35, 36, -108, -56, -14, 69, -111, 17, 45, 111, 55, 105, -61, 116, 0, -51, 5, -41, -45, 89, -41, -61, 69, -37, 94]
解密明文：[84, 104, 105, 115, 32, 105, 115, 32, -28, -72, -128, -26, -82, -75, -26, -104, -114, -26, -106, -121, -27, -122, -123, -27, -82, -71, -17, -68, -127]

  总结

  现代密码学应用中，des的身影已越来越少见，随着硬件和互联网的发展，des在安全性方面的劣势变得尤为明显。在des之后，逐渐出现了用于过渡的3des以及新一代密码算法aes，3des是为了使得des更加难以破解，使用三次des加解密叠加得到的密码算法。而aes是作为下一代对称密码学算法，使用完全不同的算法进行了实现。在实际应用中，可以根据个人所需，选择合适的算法进行应用。