Reverse public key encryption in c# and php

Question

Reverse public key encryption in c# and php

I have a c# application and a php server. The app must be activated for a fee. After activation, a request is sent to the server, in the parameters of which there is a mac-id of the computer, to which the server responds with a string in which the mac-id is encrypted. I need the server to use some secret algorithm to encrypt this mac-id so that the user can only check whether it is encrypted correctly, and cannot encrypt ITSELF, so that the program it was more resistant to hacking (the user could not encrypt his mac-id himself).

THAT IS:

the server (in php) encrypts some kind of drain with a secret key and passes it to the user
the user (in c#) can only check this string for validity ( using the public key).

Most likely this can be implemented via rsa-1, but I don't really understand how(

I will be glad to receive any hints)

2

c#php шифрование rsa

Author: user188596, 2019-10-16

Source

1 answers

score 1 · Answer 1

    internal static class  RSAcrypt
   {
       private static RSAParameters _publickey;
       private static RSAParameters _privatekey;
       /// <summary>
       /// Публичный код для шифрования
       /// </summary>
       private static string _publicKey;
       /// <summary>
       /// Частный ключ для дешефровки
       /// </summary>
       private static string _privateKey;


       public enum keySizes
       {
           Size512 = 512,
           Size1024 = 1024,
           Size2048 = 2048,
           Size952 = 952,
           Size136 = 136
       };

       /// <summary>
       /// Частный ключ для дешефровки
       /// </summary>
       public static string PrivateKey
       {
           get { return _privateKey; }
           set { _privateKey = value; }
       }

       /// <summary>
       /// Публичный код для шифрования
       /// </summary>
       public static string PublicKey
       {
           get { return _publicKey; }
           set { _publicKey = value; }
       }

       /// <summary>
       /// Метод генерирует два ключа публичный и часный и сохраняет их файлы
       /// </summary>
       public static void GenerateKeys() //создание ключей 
       {
           try
           {
               if (Directory.Exists(GlobalConfig.TempFolder) == false)
               {
                   Directory.CreateDirectory(GlobalConfig.Data);
                   Directory.CreateDirectory(GlobalConfig.TempFolder);
               }
               using (var rsa = new RSACryptoServiceProvider((int) keySizes.Size2048))
               {
                   if (File.Exists(GlobalConfig.PublicKey))
                       File.Delete(GlobalConfig.PublicKey);
                   if (File.Exists(GlobalConfig.PrivateKey))
                       File.Delete(GlobalConfig.PrivateKey);

                   rsa.PersistKeyInCsp = false;
                   PublicKey = rsa.ToXmlString(false);
                   File.WriteAllText(GlobalConfig.PublicKey, PublicKey);

                   PrivateKey = rsa.ToXmlString(true);
                   File.WriteAllText(GlobalConfig.PrivateKey, PrivateKey);
               }
           }
           catch (Exception e)
           {
               //TODO:: обработчик ошибок
           }
       }

       public static void GetKeys()
       {
           if (File.Exists(GlobalConfig.PublicKey))
           {
               PublicKey = File.ReadAllText(GlobalConfig.PublicKey);
           }
           if (File.Exists(GlobalConfig.PrivateKey))
           {
               PrivateKey = File.ReadAllText(GlobalConfig.PrivateKey);
             //  File.Delete(GlobalConfig.PrivateKey);
           }   


       }

       /// <summary>
       /// Метод дешифрует используя Часный ключ
       /// </summary>
       /// <param name="text">текс для шифрования</param>
       /// <returns></returns>
       public static string Decrypt(string text)
       {
           try
           {
               byte[] decrContent = null;

               RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
               rsa.FromXmlString(PrivateKey);
               decrContent = rsa.Decrypt(Convert.FromBase64String(text), true);
               return _toString(decrContent);
           }
           catch (Exception e)
           {
               MessageBox.Show(e.Message, @"Ошибка дешифровки", MessageBoxButtons.OK, MessageBoxIcon.Error);
               throw;
           }
       }
       /// <summary>
       /// Метод меняет кодировку
       /// </summary>
       /// <param name="decrContent">массив байтов</param>
       /// <returns></returns>
       private static string _toString(byte[] decrContent)
       {
           return Encoding.UTF8.GetString(decrContent);
       }
       /// <summary>
       /// Метод переводит String в байты
       /// </summary>
       /// <param name="text"></param>
       /// <returns></returns>
       private static byte[] _toByte(string text)
       {
           return Encoding.UTF8.GetBytes(text);
       }

       /// <summary>
       /// Метод шифрудет данные с указаным публичным  ключем
       /// </summary>
       /// <param name="text">Текс для расшидрования</param>
       /// <returns></returns>
       public static string Encrypt(string text)
       {
           try
           {
               byte[] encContent = null;

               RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
               rsa.FromXmlString(PublicKey);
               encContent = rsa.Encrypt(_toByte(text),true);
               return Convert.ToBase64String(encContent);
           }
           catch (Exception e)
           {
               Console.WriteLine(e);
               throw;
           }
       }

   }

RSA encryption