C#字符串对称加密算法

 

//对字符串进行SHA1摘要
public string EncryptToSHA1(string str)
{
            SHA1CryptoServiceProvider sha1 = new SHA1CryptoServiceProvider();
            byte[] str1 = Encoding.UTF8.GetBytes(str);
            byte[] str2 = sha1.ComputeHash(str1);
            sha1.Clear();
            (sha1 as IDisposable).Dispose();
            return Convert.ToBase64String(str2);
}

/// <summary>
        /// 加密
        /// </summary>
        /// <param name="str"></param>
        /// <param name="key"></param>
        /// <returns></returns>
        public static string Encode(string str, string key)
        {
            DESCryptoServiceProvider provider = new DESCryptoServiceProvider();
            provider.Key = Encoding.ASCII.GetBytes(key.Substring(0, 8));
            provider.IV = Encoding.ASCII.GetBytes(key.Substring(0, 8));
            byte[] bytes = Encoding.GetEncoding("UTF-8").GetBytes(str);
            MemoryStream stream = new MemoryStream();
            CryptoStream stream2 = new CryptoStream(stream, provider.CreateEncryptor(), CryptoStreamMode.Write);
            stream2.Write(bytes, 0, bytes.Length);
            stream2.FlushFinalBlock();
            StringBuilder builder = new StringBuilder();
            foreach (byte num in stream.ToArray())
            {
                builder.AppendFormat("{0:X2}", num);
            }
            stream.Close();
            return builder.ToString();
        }

        /// <summary>
        /// Des 解密 GB2312
        /// </summary>
        /// <param name="str">Desc string</param>
        /// <param name="key">Key ,必须为8位 </param>
        /// <returns></returns>
        public static string Decode(string str, string key)
        {
            DESCryptoServiceProvider provider = new DESCryptoServiceProvider();
            provider.Key = Encoding.ASCII.GetBytes(key.Substring(0, 8));
            provider.IV = Encoding.ASCII.GetBytes(key.Substring(0, 8));
            byte[] buffer = new byte[str.Length / 2];
            for (int i = 0; i < (str.Length / 2); i++)
            {
                int num2 = Convert.ToInt32(str.Substring(i * 2, 2), 0x10);
                buffer[i] = (byte)num2;
            }
            MemoryStream stream = new MemoryStream();
            CryptoStream stream2 = new CryptoStream(stream, provider.CreateDecryptor(), CryptoStreamMode.Write);
            stream2.Write(buffer, 0, buffer.Length);
            stream2.FlushFinalBlock();
            stream.Close();
            return Encoding.GetEncoding("UTF-8").GetString(stream.ToArray());
        }