C#des加密算法指定键的大小对于此算法无效

api接口调用的时候，需要和java的进行加密通信，通信过程中用到DES加密，java那边DES的key为64位字符串，而之前c#的DES加密是key为8位

DESCryptoServiceProvider 中的密钥是8位；
RijndaelManaged 中的密钥是32位。

java中的的DES/CBC/PKCS5Padding对应c#中的DES/CBC/PKCS7

对应的javaDES加密函数：因为要网络传输，把+号全部转为%2B

    private static final String KEY ="xxxJE234D";//64个字符串
    public static String encryptString(String plaintext) throws Exception{
        Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
        DESKeySpec desKeySpec = new DESKeySpec(KEY.getBytes("UTF-8"));
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
        SecretKey secretKey = keyFactory.generateSecret(desKeySpec);
        IvParameterSpec iv = new IvParameterSpec(KEY.substring(0, 8).getBytes("UTF-8"));
        cipher.init(Cipher.ENCRYPT_MODE, secretKey, iv);
        byte[] bt = cipher.doFinal(plaintext.getBytes("UTF-8"));
        String strs = new BASE64Encoder().encode(bt).replaceAll("[+]", "%2B");
        return strs;
    }

c#对应的DES加密函数：

    public static string ToEncrypt2(string str, string myKey)
        {
            string encryptKeyall = Convert.ToString(myKey);    //定义密钥  
            if (encryptKeyall.Length < 9)
            {
                for (; ; )
                {
                    if (encryptKeyall.Length < 9)
                        encryptKeyall += encryptKeyall;
                    else
                        break;
                }
            }
            string encryptKey = encryptKeyall.Substring(0, 8);
            DESCryptoServiceProvider descsp = new DESCryptoServiceProvider();   //实例化加/解密类对象   
            descsp.Mode = CipherMode.CBC;
            descsp.Padding = PaddingMode.PKCS7;
            byte[] key = Encoding.UTF8.GetBytes(encryptKey); //定义字节数组，用来存储密钥    
            byte[] data = Encoding.UTF8.GetBytes(str);//定义字节数组，用来存储要加密的字符串  
            MemoryStream MStream = new MemoryStream(); //实例化内存流对象      
            //使用内存流实例化加密流对象   
            CryptoStream CStream = new CryptoStream(MStream, descsp.CreateEncryptor(key, key), CryptoStreamMode.Write);
            CStream.Write(data, 0, data.Length);  //向加密流中写入数据      
            CStream.FlushFinalBlock();              //释放加密流      
            return Convert.ToBase64String(MStream.ToArray()).Replace("+", "%2B");//返回加密后的字符串  
        }

c#中key为8位的情况:

  public static string Encrypt(string pToEncrypt, string sKey)
        {
            using (DESCryptoServiceProvider des = new DESCryptoServiceProvider())
            {

                byte[] inputByteArray = Encoding.UTF8.GetBytes(pToEncrypt);
                des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
                des.IV = ASCIIEncoding.ASCII.GetBytes(sKey);
                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                using (CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write))
                {
                    cs.Write(inputByteArray, 0, inputByteArray.Length);
                    cs.FlushFinalBlock();
                    cs.Close();
                }
                string str = Convert.ToBase64String(ms.ToArray());
                ms.Close();
                return str;
            }
        }
//解密
    /// <summary>
        /// 进行DES解密
        /// </summary>
        /// <param name="pToDecrypt">要解密的以Base64</param>
        /// <param name="sKey">密钥，且必须为8位</param>
        /// <returns>已解密的字符串</returns>
        public static string Decrypt(string pToDecrypt, string sKey)
        {
            byte[] inputByteArray = Convert.FromBase64String(pToDecrypt);
            using (DESCryptoServiceProvider des = new DESCryptoServiceProvider())
            {

                des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
                des.IV = ASCIIEncoding.ASCII.GetBytes(sKey);
                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                using (CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write))
                {
                    cs.Write(inputByteArray, 0, inputByteArray.Length);
                    cs.FlushFinalBlock();
                    cs.Close();
                }
                string str = Encoding.UTF8.GetString(ms.ToArray());
                ms.Close();
                return str;
            }
        }