Uses  JwaWinCrypt, JwaWinError, EncdDecd;

Type
  TSignedData = record
    SignSize: Cardinal;
    Sign: PChar;
  end;

function SignData(Data: PChar): TSignedData;
var
  Cert: TProperCertificate;  // Cert.pCert: PCERT_CONTEXT;
  SignPara: CRYPT_SIGN_MESSAGE_PARA;
  Error, DataSize: DWORD;
  pbArray, cbArray: Pointer;
begin
  // Тут получение сертификата Cert ...
  
  DataSize := Length(Data);
  pbArray   := @Data;
  cbArray   := @DataSize;

  ZeroMemory(@SignPara, SizeOf(CRYPT_SIGN_MESSAGE_PARA));
  with SignPara do
  begin
    cbSize := SizeOf(SignPara);
    dwMsgEncodingType := X509_ASN_ENCODING or PKCS_7_ASN_ENCODING; 
    pSigningCert := Cert.pCert;
    HashAlgorithm.pszObjId := '1.2.643.2.2.9';  //  GOST R 34.11-94	длина ключа - 256 бит	ID: 32798
    HashAlgorithm.Parameters.cbData := 0;
    pvHashAuxInfo := nil;
    cMsgCert := 1;
    rgpMsgCert := @Cert.pCert;
    cMsgCrl := 0;
    rgpMsgCrl := nil;
    cAuthAttr := 0;
    rgAuthAttr := nil;
    cUnauthAttr := 0;
    rgUnauthAttr := nil;
    dwFlags := 0;
    dwInnerContentType := 0;
  end;

  CryptSignMessage(@SignPara, False, 1, pbArray, cbArray, nil, Result.SignSize);
  GetMem(Result.Sign, Result.SignSize);
  CryptSignMessage(@SignPara, False, 1, pbArray, cbArray, PByte(Result.Sign), Result.SignSize);
end;