//создание подписи
        public byte[] Sign(byte[] body)
        {
            X509Certificate2 signerCert = GetSignerCert();
            if (signerCert == null)
                return null;
            var contentInfo = new ContentInfo(body);
            
            var signedCms = new SignedCms(contentInfo, true);

            var cmsSigner = new CmsSigner(signerCert);
            
            try
            {
                signedCms.ComputeSignature(cmsSigner, false);
            }
            catch (CryptographicException crex)
            {

            }
            finally
            {
                SafeClose();
            }
                        
            // Кодируем CMS/PKCS #7 подпись сообщения.
            return signedCms.Encode();
        }