加解密（校验哈希值、MD5值）

1、计算文本哈希值：

public static string ComputeHash(string password)
    {
        byte[] buffer = System.Text.Encoding.UTF8.GetBytes(password);
        SHA1CryptoServiceProvider sha = new SHA1CryptoServiceProvider();
        byte[] hash = sha.ComputeHash(buffer);
        StringBuilder passwordbullder = new StringBuilder(32);
        foreach (byte hashByte in hash)
        {
            passwordbullder.Append(hashByte.ToString("x2"));

        }
        return passwordbullder.ToString();
    }

2、计算文件的哈希值、MD5：

            FileStream fs = new FileStream(this.fileFullName, FileMode.Open, FileAccess.Read);
            SHA1CryptoServiceProvider sha1 = new SHA1CryptoServiceProvider();
            Byte[] fileHashes_SHA1 = sha1.ComputeHash(fs);
            MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
            Byte[] fileHashes_MD5 = md5.ComputeHash(fs);
            //this.fileSize = fs.Length;
            //this.sendSize = 0;
            fs.Close();
            fs.Dispose();

　　3、解密字符串

   /// <summary>
        /// 解密字符串。
        /// </summary>
        /// <param name="sourceString">要解密的字符串。</param>
        /// <param name="encryptionKey">密钥。</param>
        /// <returns>解密后的字符串。</returns>
        private String DecryptString(String sourceString, String encryptionKey)
        {
            try
            {
                Byte[] rgbKey = Encoding.UTF8.GetBytes(encryptionKey.Substring(0, 8));
                Byte[] rgbIV = this.iv;     //默认初始化密钥向量{ 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };
                Byte[] inputByteArray = Convert.FromBase64String(sourceString);
                DESCryptoServiceProvider des = new DESCryptoServiceProvider();
                MemoryStream ms = new MemoryStream();
                CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
                cs.Write(inputByteArray, 0, inputByteArray.Length);
                cs.FlushFinalBlock();
                return Encoding.UTF8.GetString(ms.ToArray());
            }
            catch
            {
                return String.Empty;
            }
        }

获取MD5密文：

public static string GetMd5Hash(string input)
        {
            MD5 md5Hasher = MD5.Create();

            byte[] data = md5Hasher.ComputeHash(Encoding.Default.GetBytes(input));

            StringBuilder sBuilder = new StringBuilder();

            for (int i = 0; i < data.Length; i++)
            {
                sBuilder.Append(data[i].ToString("x2"));
            }
            return sBuilder.ToString();
        }