关于DES 历程密钥和密钥分散

关于DES 过程密钥和密钥分散
目前要做个项目 涉及到过程密钥及密钥分散，我想问下过程密钥、密钥分散的含义分别是什么，请举例说明
[解决办法]
  public class DES
        {
            //默认密钥向量
            private static byte[] Keys = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };

            /// <summary>
            /// DES加密字符串
            /// </summary>
            /// <param name="encryptString">待加密的字符串</param>
            /// <param name="encryptKey">加密密钥,要求为8位</param>
            /// <returns>加密成功返回加密后的字符串,失败返回源串</returns>
            public static string Encode(string encryptString, string encryptKey)
            {
                encryptKey = GF_GET.GetSubString(encryptKey, 8, "");
                encryptKey = encryptKey.PadRight(8, ' ');
                byte[] rgbKey = Encoding.UTF8.GetBytes(encryptKey.Substring(0, 8));
                byte[] rgbIV = Keys;
                byte[] inputByteArray = Encoding.UTF8.GetBytes(encryptString);
                DESCryptoServiceProvider dCSP = new DESCryptoServiceProvider();
                MemoryStream mStream = new MemoryStream();

                CryptoStream cStream = new CryptoStream(mStream, dCSP.CreateEncryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
                cStream.Write(inputByteArray, 0, inputByteArray.Length);
                cStream.FlushFinalBlock();
                return Convert.ToBase64String(mStream.ToArray());

            }

            /// <summary>
            /// DES解密字符串
            /// </summary>
            /// <param name="decryptString">待解密的字符串</param>
            /// <param name="decryptKey">解密密钥,要求为8位,和加密密钥相同</param>
            /// <returns>解密成功返回解密后的字符串,失败返源串</returns>
            public static string Decode(string decryptString, string decryptKey)
            {
                try
                {
                    decryptKey = GF_GET.GetSubString(decryptKey, 8, "");
                    decryptKey = decryptKey.PadRight(8, ' ');
                    byte[] rgbKey = Encoding.UTF8.GetBytes(decryptKey);
                    byte[] rgbIV = Keys;
                    byte[] inputByteArray = Convert.FromBase64String(decryptString);
                    DESCryptoServiceProvider DCSP = new DESCryptoServiceProvider();

                    MemoryStream mStream = new MemoryStream();
                    CryptoStream cStream = new CryptoStream(mStream, DCSP.CreateDecryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
                    cStream.Write(inputByteArray, 0, inputByteArray.Length);
                    cStream.FlushFinalBlock();
                    return Encoding.UTF8.GetString(mStream.ToArray());
                }
                catch
                {
                    return "";
                }
            }
        }