string ContainerPass = <пароль>;

         ...
        
        private static void FillcontainerPassword(X509Certificate2 certificate2)
        {
            var provider = (Gost3410CryptoServiceProvider)certificate2.PrivateKey;
            var secure = new SecureString();

            // заполняем пароль для контейнера, хранящего сертификат
            foreach (char charPass in ContainerPass)
            {
                secure.AppendChar(charPass);
            } 
//            secure.AppendChar('c');//ложный символ в пароль для проверки на false
            provider.SetContainerPassword(secure);
            CheckPassword(provider);
        }

        ...

        private static bool CheckPassword(Gost3410CryptoServiceProvider provider)
        {
            var encoding = new System.Text.UTF8Encoding();
            byte[] passBytes = encoding.GetBytes(ContainerPass);
            byte[] dummyHash = new byte[32];
            Array.Copy(passBytes, dummyHash, passBytes.Length);
            
            byte[] signHash = provider.SignHash(dummyHash);
            bool result = provider.VerifyHash(dummyHash, signHash);

            return result;
        }

byte[] signHash = provider.SignHash(dummyHash);