詳解DES加密算法及在Java程序中的使用示例

DES加密算法
DES全稱為Data Encryption Standard，即數據加密標準，是一種使用密鑰加密的塊算法，1976年被美國聯邦政府的國家標準局確定為聯邦資料處理標準（FIPS），隨後在國際上廣泛流傳開來。
DES算法的入口參數有三個:Key、Data、Mode。其中Key為7個字節共56位,是DES算法的工作密鑰;Data為8個字節64位,是要被加密或被解密的數據;Mode為DES的工作方式,有兩種:加密或解密。
DES算法把64位的明文輸入塊變為64位的密文輸出塊,它所使用的密鑰也是56位，其算法主要分為兩步：
1）初始置換其功能是把輸入的64位數據塊按位重新組合,並把輸出分為L0、R0兩部分,每部分各長32位,其置換規則為將輸入的第58位換到第一位,第50位換到第2位……依此類推,最後一位是原來的第7位。 L0、R0則是換位輸出後的兩部分，L0是輸出的左32位,R0是右32位,例:設置換前的輸入值為D1D2D3……D64,則經過初始置換後的結果為:L0=D58D50……D8;R0=D57D49……D7。
其置換規則見下表：

 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）逆置換經過16次迭代運算後,得到L16、R16,將此作為輸入,進行逆置換,逆置換正好是初始置換的逆運算，由此即得到密文輸出。
此算法是對稱加密算法體系中的代表,在計算機網絡系統中廣泛使用.

Java基本實現

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美國IBM研製，對稱加密算法*/ public class DES { // 算法名稱public static final String KEY_ALGORITHM = "DES"; // 算法名稱/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 * 密鑰生成器生成密鑰* 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 * 使用密鑰工廠生成密鑰，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(); } /** * 生成密鑰* * @return * @throws Exception */ private static byte[] generateKey() throws Exception { KeyGenerator keyGenerator = KeyGenerator.getInstance(KEY_ALGORITHM); keyGenerator.init(56); //des 必須是56, 此初始方法不必須調用SecretKey secretKey = keyGenerator.generateKey(); return secretKey.getEncoded(); } /** * 還原密鑰* * @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實現：

 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 { // 算法名稱public static final String KEY_ALGORITHM = "DESede"; // 算法名稱/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("加密後：" + new String(encryptData)); System.out.println("解密後："+ new String(tripleDES.decrypt(encryptData))); tripleDES = new TripleDES("CBC"); tripleDES.encrypt2("sau8jzxlc DQV#><«|vm,'123`98(*^&%^^JCB ZX>>A<S<}}{"); System.out.println("加密後：" + new String(encryptData)); System.out.println("解密後："+ 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); } }