Crypto.CERT_CONTEXT Cert;
           IntPtr pCert;
            Crypto.CERT_CONTEXT* pCertContext = &Cert;

            pCert = new IntPtr((void*)pCertContext);

                res = Crypto.CryptVerifyDetachedMessageSignature(
                ref VerifyParams,
                0,
                pbDetachedSignBlob,  // детачед подпись
                cbDetachedSignBlob,  // размер подписи
                1,  // кол-во блоков данных
                rgpbToBeSigned,
                rgcbToBeSigned,
                //IntPtr.Zero          // Pointer to signer certificate.
                 pCert
                );

                Cert = (Crypto.CERT_CONTEXT)Marshal.PtrToStructure(pCert, typeof(Скнзещ.CERT_CONTEXT)); 

                    IntPtr pCertInfo;
                    pCertInfo = Cert.pCertInfo;
                    
                    Crypto.CERT_INFO cert_info = new Crypto.CERT_INFO();

////////  здесь ошибка   ex.Message = "В экземпляре объекта не задана ссылка на объект."
  cert_info = (Crypto.CERT_INFO)Marshal.PtrToStructure(pCertInfo, typeof(Crypto.CERT_INFO));

pCert = (IntPtr)Marshal.PtrToStructure(ppCert, typeof(IntPtr));                     
Cert = (Crypto.CERT_CONTEXT)Marshal.PtrToStructure(pCert, typeof(Crypto.CERT_CONTEXT)); 
IntPtr pCertInfo;
pCertInfo = Cert.pCertInfo;
Crypto.CERT_INFO cert_info = new Crypto.CERT_INFO();
cert_info = (Crypto.CERT_INFO)Marshal.PtrToStructure(pCertInfo, typeof(Crypto.CERT_INFO));
byte[] bSubj = new byte[cert_info.Subject.cbData];
Marshal.Copy(cert_info.Subject.pbData, bSubj, 0, cert_info.Subject.cbData);
encoding = System.Text.Encoding.GetEncoding("UTF-8");
string s1;
s1 = encoding.GetString(bSubj);