var
  hProv: HCRYPTPROV;
  hStore: HCERTSTORE;
  hPublicKey: HCRYPTKEY;
  pCert: PCCERT_CONTEXT;
  dwCertEncType, dwKeySpec: DWORD;
  KeyStream: TBytesStream;
begin
  dwCertEncType := X509_ASN_ENCODING;
  KeyStream := TBytesStream.Create;
  try
    hStore := CertOpenSystemStore(0, 'ADDRESSBOOK');
    try
      pCert := CertFindCertificateInStore(hStore, dwCertEncType, 0, CERT_FIND_SUBJECT_STR, @Certificate[1], nil);
    finally
      CertCloseStore(hStore, 0);
    end;

    if Assigned(pCert) then
    begin
      CryptAcquireContext(hProv, null, @Provider[1], PROV_GOST_2001_DH, 0);
      try
        CryptImportKey(hProv, ?, ?, hKey, 0, hPublicKey);
      finally
        CryptDestroyKey(hPublicKey);
        CertFreeCertificateContext(pCert);
        CryptReleaseContext(hProv, 0);
      end;
    end;
  finally
    KeyStream.Free;
  end;