DES算法简介
DES 算法
DES算法为密码体制中的对称密码体制，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体制加密算法。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。
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