详解DES加密算法及在Java程序中的使用示例

DES加密算法
DES全称为Data Encryption Standard，即数据加密标准，是一种使用密钥加密的块算法，1976年被美国联邦政府的国家标准局确定为联邦资料处理标准（FIPS），随后在国际上广泛流传开来。
DES算法的入口参数有三个:Key、Data、Mode。其中Key为7个字节共56位,是DES算法的工作密钥;Data为8个字节64位,是要被加密或被解密的数据;Mode为DES的工作方式,有两种:加密或解密。
DES算法把64位的明文输入块变为64位的密文输出块,它所使用的密钥也是56位，其算法主要分为两步：
1）初始置换
其功能是把输入的64位数据块按位重新组合,并把输出分为L0、R0两部分,每部分各长32位,其置换规则为将输入的第58位换到第一位,第50位换到第2位……依此类推,最后一位是原来的第7位。L0、R0则是换位输出后的两部分，L0是输出的左32位,R0是右32位,例:设置换前的输入值为D1D2D3……D64,则经过初始置换后的结果为:L0=D58D50……D8;R0=D57D49……D7。
其置换规则见下表：

58,50,42,34,26,18,10,2,60,52,44,36,28,20,12,4,
62,54,46,38,30,22,14,6,64,56,48,40,32,24,16,8,
57,49,41,33,25,17,9,1,59,51,43,35,27,19,11,3,
61,53,45,37,29,21,13,5,63,55,47,39,31,23,15,7,

2）逆置换
经过16次迭代运算后,得到L16、R16,将此作为输入,进行逆置换,逆置换正好是初始置换的逆运算，由此即得到密文输出。
此算法是对称加密算法体系中的代表,在计算机网络系统中广泛使用.

Java基本实现

package com.stone.security; 
 
import java.security.Key; 
import java.security.SecureRandom; 
 
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.IvParameterSpec; 
 
/** 
 * DES 算法    1972美国IBM研制，对称加密算法 
 */ 
public class DES {  
  // 算法名称 
  public static final String KEY_ALGORITHM = "DES"; 
  // 算法名称/加密模式/填充方式 
  public static final String CIPHER_ALGORITHM_ECB = "DES/ECB/PKCS5Padding"; 
  public static final String CIPHER_ALGORITHM_CBC = "DES/CBC/PKCS5Padding"; 
   
  public static void main(String[] args) throws Exception { 
    /* 
     * 使用 ECB mode 
     * 密钥生成器 生成密钥 
     * ECB mode cannot use IV 
     */ 
    byte[] key = generateKey();  
    byte[] encrypt = encrypt("胃炎F#*（x）".getBytes(), key); 
    System.out.println(new String(decrypt(encrypt, key))); 
     
     
    /* 
     * 使用CBC mode 
     * 使用密钥工厂生成密钥，加密 解密 
     * iv: DES in CBC mode and RSA ciphers with OAEP encoding operation. 
     */ 
    DESKeySpec dks = new DESKeySpec(generateKey()); 
    SecretKeyFactory factory = SecretKeyFactory.getInstance(KEY_ALGORITHM); 
    SecretKey secretKey = factory.generateSecret(dks); 
    Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM_CBC); 
    cipher.init(Cipher.ENCRYPT_MODE, secretKey, new IvParameterSpec(getIV())); 
    byte[] enc = cipher.doFinal("胃炎A%F#*（x）".getBytes()); //加密 
     
    cipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(getIV())); 
    byte[] dec = cipher.doFinal(enc); // 解密 
    System.out.println(new String(dec)); 
  } 
   
  static byte[] getIV() { 
    String iv = "asdfivh7"; //IV length: must be 8 bytes long 
    return iv.getBytes(); 
  } 
 
  /** 
   * 生成密钥 
   * 
   * @return 
   * @throws Exception 
   */ 
  private static byte[] generateKey() throws Exception { 
    KeyGenerator keyGenerator = KeyGenerator.getInstance(KEY_ALGORITHM); 
    keyGenerator.init(56); //des 必须是56, 此初始方法不必须调用 
    SecretKey secretKey = keyGenerator.generateKey(); 
    return secretKey.getEncoded(); 
  } 
 
  /** 
   * 还原密钥 
   * 
   * @param key 
   * @return 
   * @throws Exception 
   */ 
  private static Key toKey(byte[] key) throws Exception { 
    DESKeySpec des = new DESKeySpec(key); 
    SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(KEY_ALGORITHM); 
    SecretKey secretKey = keyFactory.generateSecret(des); 
    return secretKey; 
  } 
   
  /** 
   * 加密 
   * @param data 原文 
   * @param key 
   * @return 密文 
   * @throws Exception 
   */ 
  public static byte[] encrypt(byte[] data, byte[] key) throws Exception { 
    Key k = toKey(key); 
    Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM_ECB); 
    cipher.init(Cipher.ENCRYPT_MODE, k, new SecureRandom()); 
    return cipher.doFinal(data); 
  } 
  /** 
   * 解密 
   * @param data 密文 
   * @param key 
   * @return 明文、原文 
   * @throws Exception 
   */ 
  public static byte[] decrypt(byte[] data, byte[] key) throws Exception { 
    Key k = toKey(key); 
    Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM_ECB); 
    cipher.init(Cipher.DECRYPT_MODE, k, new SecureRandom()); 
    return cipher.doFinal(data); 
  } 
} 

Java三重DES实现：

package com.stone.security; 
 
import javax.crypto.Cipher; 
import javax.crypto.KeyGenerator; 
import javax.crypto.SecretKey; 
import javax.crypto.SecretKeyFactory; 
import javax.crypto.spec.DESedeKeySpec; 
import javax.crypto.spec.IvParameterSpec; 
 
/** 
 * 三重加密 3DES也作 Triple DES, 
 */ 
public class TripleDES { 
  // 算法名称 
  public static final String KEY_ALGORITHM = "DESede"; 
  // 算法名称/加密模式/填充方式 
  public static final String CIPHER_ALGORITHM_ECB = "DESede/ECB/PKCS5Padding"; 
  public static final String CIPHER_ALGORITHM_CBC = "DESede/CBC/PKCS5Padding"; 
   
  private KeyGenerator keyGen; 
  private SecretKey secretKey; 
  private SecretKey secretKey2; 
  private Cipher cipher; 
  private static byte[] encryptData; 
   
  public static void main(String[] args) throws Exception { 
    TripleDES tripleDES = new TripleDES("ECB"); 
    tripleDES.encrypt("sau8jzxlcvm,'123`98(*^&%^^JCB ZX>>A<S<}}{"); 
    System.out.println("加密后：" + new String(encryptData)); 
    System.out.println("解密后："+ new String(tripleDES.decrypt(encryptData))); 
     
    tripleDES = new TripleDES("CBC"); 
    tripleDES.encrypt2("sau8jzxlc DQV#><«|vm,'123`98(*^&%^^JCB ZX>>A<S<}}{"); 
    System.out.println("加密后：" + new String(encryptData)); 
    System.out.println("解密后："+ new String(tripleDES.decrypt2(encryptData))); 
  } 
   
  public TripleDES(String mode) throws Exception { 
    if ("ECB".equals(mode)) { 
//     cipher = Cipher.getInstance(KEY_ALGORITHM); 
      cipher = Cipher.getInstance(CIPHER_ALGORITHM_ECB); 
      keyGen = KeyGenerator.getInstance(KEY_ALGORITHM); 
      secretKey = keyGen.generateKey(); 
    } else if("CBC".equals(mode)) { 
      cipher = Cipher.getInstance(CIPHER_ALGORITHM_CBC); 
      keyGen = KeyGenerator.getInstance(KEY_ALGORITHM); 
      DESedeKeySpec spec = new DESedeKeySpec(keyGen.generateKey().getEncoded()); 
      secretKey2 = SecretKeyFactory.getInstance(KEY_ALGORITHM).generateSecret(spec); 
    } 
  } 
  /** 
   * 加密 
   * @param str 
   * @return 
   * @throws Exception 
   */ 
  public byte[] encrypt(String str) throws Exception { 
    cipher.init(Cipher.ENCRYPT_MODE, secretKey); 
    return encryptData = cipher.doFinal(str.getBytes()); 
  } 
  /** 
   * 解密 
   * @param encrypt 
   * @return 
   * @throws Exception 
   */ 
  public byte[] decrypt(byte[] encrypt) throws Exception { 
    cipher.init(Cipher.DECRYPT_MODE, secretKey); 
    return encryptData = cipher.doFinal(encrypt); 
  } 
  byte[] getIV() { 
    return "administ".getBytes(); 
  } 
  /** 
   * 加密 
   * @param str 
   * @return 
   * @throws Exception 
   */ 
  public byte[] encrypt2(String str) throws Exception { 
    cipher.init(Cipher.ENCRYPT_MODE, secretKey2, new IvParameterSpec(getIV())); 
    return encryptData = cipher.doFinal(str.getBytes()); 
  } 
  /** 
   * 解密 
   * @param encrypt 
   * @return 
   * @throws Exception 
   */ 
  public byte[] decrypt2(byte[] encrypt) throws Exception { 
    cipher.init(Cipher.DECRYPT_MODE, secretKey2, new IvParameterSpec(getIV())); 
    return encryptData = cipher.doFinal(encrypt); 
  } 
} 

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