cspParameters.Flags = CspProviderFlags.NoPrompt | CspProviderFlags.UseMachineKeyStore

        
         internal X509Certificate2 GetCertificate()
        {
            //true - MachineKeyStore; false - UserKeyStore
            _provider = BuildCryptoProviderByKeyStore(false) ?? BuildCryptoProviderByKeyStore(true);

            if (_provider == null)
            {
                throw new Exception("... текст ...");
            }
            CheckCertificatePassword(_provider);
            return GetX509Certificate2(_provider);
        }
         ...

        private Gost3410CryptoServiceProvider BuildCryptoProviderByKeyStore(bool isMachineKeyStore)
        {
            CspParameters cspParameters = BuildCertificateCspParameters(isMachineKeyStore); // открываем контейнер.
            try
            {
                _provider = new Gost3410CryptoServiceProvider(cspParameters);
                return _provider;
            }
            catch (Exception)
            {
                return null; //крипто-провайдер не создан
            }
        }
         ...

        //конфигурация для Gost3410CryptoServiceProvider
        private CspParameters BuildCertificateCspParameters(bool isMachineKeyStore)
        {
            var cspParameters = new CspParameters();
            cspParameters.KeyContainerName = _сontainerName; //имя используемого контейнера
            cspParameters.ProviderType = 75; //номер Crypto-Pro GOST R 34.10-2001 Cryptographic Service Provider
            cspParameters.Flags = isMachineKeyStore
                                      ? (CspProviderFlags.NoPrompt|CspProviderFlags.UseExistingKey|CspProviderFlags.UseMachineKeyStore)
                                      : (CspProviderFlags.NoPrompt|CspProviderFlags.UseExistingKey);
            cspParameters.KeyPassword = BuildCspParametersPassword();
            return cspParameters;
        }
         ...

        //присвоение пароля
        private SecureString BuildCspParametersPassword()
        {
            var secure = new SecureString();
            foreach (char charPass in _сontainerPass)
            {
                secure.AppendChar(charPass);
            }
            return secure;
        }
         ...

        //проверка пароля контейнера
        private static void CheckCertificatePassword(Gost3410CryptoServiceProvider provider)
        {
            var dummyHash = new byte[32];
            try
            {
                provider.SignHash(dummyHash); //если ошибка - пароль не верный
            }
            catch (Exception)
            {
                throw new Exception("... текст ...");
            }
        }
         ...

        // достаем сертификат из контейнера
        private static X509Certificate2 GetX509Certificate2(Gost3410CryptoServiceProvider provider)
        {
            X509Certificate2 certificate2 = provider.ContainerCertificate;
            if (certificate2 == null)
            {
                throw new Exception("... текст ...");
            }
            return certificate2;
        }