Android数据加密之Des加密详解

  private final static String HEX = "0123456789ABCDEF";
  private final static String TRANSFORMATION = "DES/CBC/PKCS5Padding";//DES是加密方式 CBC是工作模式 PKCS5Padding是填充模式
  private final static String IVPARAMETERSPEC = "01020304";////初始化向量参数，AES 为16bytes. DES 为8bytes.
  private final static String ALGORITHM = "DES";//DES是加密方式
  private static final String SHA1PRNG = "SHA1PRNG";//// SHA1PRNG 强随机种子算法, 要区别4.2以上版本的调用方法 

 /*
 * 生成随机数，可以当做动态的密钥 加密和解密的密钥必须一致，不然将不能解密
 */
 public static String generateKey() {
  try {
   SecureRandom localSecureRandom = SecureRandom.getInstance(SHA1PRNG);
   byte[] bytes_key = new byte[20];
   localSecureRandom.nextBytes(bytes_key);
   String str_key = toHex(bytes_key);
   return str_key;
  } catch (Exception e) {
   e.printStackTrace();
  }
  return null;
 }

 //二进制转字符
 public static String toHex(byte[] buf) {
  if (buf == null)
   return "";
  StringBuffer result = new StringBuffer(2 * buf.length);
  for (int i = 0; i < buf.length; i++) {
   appendHex(result, buf[i]);
  }
  return result.toString();
 }

 private static void appendHex(StringBuffer sb, byte b) {
  sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
 } 

 // 对密钥进行处理
 private static Key getRawKey(String key) throws Exception {
  KeyGenerator kgen = KeyGenerator.getInstance(ALGORITHM);
  //for android
  SecureRandom sr = null;
  // 在4.2以上版本中，SecureRandom获取方式发生了改变
  if (android.os.Build.VERSION.SDK_INT >= 17) {
   sr = SecureRandom.getInstance(SHA1PRNG, "Crypto");
  } else {
   sr = SecureRandom.getInstance(SHA1PRNG);
  }
  // for Java
  // secureRandom = SecureRandom.getInstance(SHA1PRNG);
  sr.setSeed(key.getBytes());
  kgen.init(64, sr); //DES固定格式为64bits，即8bytes。
  SecretKey skey = kgen.generateKey();
  byte[] raw = skey.getEncoded();
  return new SecretKeySpec(raw, ALGORITHM);
 } 

 // 对密钥进行处理
 private static Key getRawKey(String key) throws Exception {
  DESKeySpec dks = new DESKeySpec(key.getBytes());
  SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
  return keyFactory.generateSecret(dks);
 } 

 /**
  * DES算法，加密
  *
  * @param data 待加密字符串
  * @param key 加密私钥，长度不能够小于8位
  * @return 加密后的字节数组，一般结合Base64编码使用
  */
 public static String encode(String key, String data) {
  return encode(key, data.getBytes());
 }


 /**
  * DES算法，加密
  *
  * @param data 待加密字符串
  * @param key 加密私钥，长度不能够小于8位
  * @return 加密后的字节数组，一般结合Base64编码使用
  */

 public static String encode(String key, byte[] data) {
  try {
   Cipher cipher = Cipher.getInstance(TRANSFORMATION);
   IvParameterSpec iv = new IvParameterSpec(IVPARAMETERSPEC.getBytes());
   cipher.init(Cipher.ENCRYPT_MODE, getRawKey(key), iv);
   byte[] bytes = cipher.doFinal(data);
   return Base64.encodeToString(bytes, Base64.DEFAULT);
  } catch (Exception e) {
   return null;
  }
 } 

 /**
  * 获取编码后的值
  *
  * @param key
  * @param data
  * @return
  */
 public static String decode(String key, String data) {
  return decode(key, Base64.decode(data, Base64.DEFAULT));
 }

 /**
  * DES算法，解密
  *
  * @param data 待解密字符串
  * @param key 解密私钥，长度不能够小于8位
  * @return 解密后的字节数组
  */
 public static String decode(String key, byte[] data) {
  try {
   Cipher cipher = Cipher.getInstance(TRANSFORMATION);
   IvParameterSpec iv = new IvParameterSpec(IVPARAMETERSPEC.getBytes());
   cipher.init(Cipher.DECRYPT_MODE, getRawKey(key), iv);
   byte[] original = cipher.doFinal(data);
   String originalString = new String(original);
   return originalString;
  } catch (Exception e) {
   return null;
  }
 }