Pascal (Lazarus/Delphi)

Sign PDF: Choosing RSASSA-PSS or PKCS1-v1_5 and Hash Algorithm

See more PDF Signatures Examples

This example demonstrates how to choose between RSASSA-PSS vs. PKCS1-v1_5 and the hash algorithm when signing a PDF. Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Pdf,
  Chilkat.Cert,
  Chilkat.JsonObject;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  pdf: TPdf;
  json: TJsonObject;
  cert: TCert;

begin
  success := False;

  //  This example requires the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  pdf := TPdf.Create;

  //  Load a PDF to be signed.
  //  The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
  success := pdf.LoadFile('qa_data/pdf/hello.pdf');
  if (success = False) then
    begin
      WriteLn(pdf.LastErrorText);
      Exit;
    end;

  //  Options for signing are specified in JSON.
  json := TJsonObject.Create;

  //  In most cases, the signingCertificateV2 attribute is needed.
  json.UpdateInt('signingCertificateV2',1);

  //  ---------------------------------------------------------------------------------------------------------------------------
  //  This example is the same as the example at Sign a PDF (Simplest Example Possible)
  //  but with the following lines added to specify the signature scheme and hash algorithm.

  //  The signature schemes PKCS-v1_5 and RSASSA-PSS have differences. 
  //  PKCSV1_5 is deterministic. The same message and key will produce an identical signature value each time. 
  //  PSS is randomized and will produce a different signature value each time.

  //  To choose the hash algorithm:
  //  (The typical choices are sha1, sha256, sha384, and sha512.)
  json.UpdateString('hashAlgorithm','sha256');

  //  To choose PKCSV1_5:
  json.UpdateString('signingAlgorithm','pkcs');
  //  Alternatively, to choose RSASSA-PSS:
  json.UpdateString('signingAlgorithm','pss');

  //  If not specified, the default is SHA256 with PKCS-v1_5.

  //  The remainder of this example is the same as the example at Sign a PDF (Simplest Example Possible)
  //  ---------------------------------------------------------------------------------------------------------------------------

  //  Put the signature on page 1, top left
  json.UpdateInt('page',1);
  json.UpdateString('appearance.y','top');
  json.UpdateString('appearance.x','left');

  //  Use a font scale of 10.0
  json.UpdateString('appearance.fontScale','10.0');

  //  In this example, the appearance of the digital signature will contain three lines:
  //  1) The signing certificate's common name
  //  2) The current date/time
  //  3) Some arbitrary text.
  //  The keyword "cert_cn" is replaced with the Certificate's Subject Common Name.
  //  The keyword "current_dt" is replaced with the current date/time.
  //  Any number of appearance text lines can be added.
  json.UpdateString('appearance.text[0]','Digitally signed by: cert_cn');
  json.UpdateString('appearance.text[1]','current_dt');
  json.UpdateString('appearance.text[2]','The crazy brown fox jumps over the lazy dog.');

  //  Load the signing certificate. (Use your own certificate.)
  cert := TCert.Create;
  success := cert.LoadPfxFile('qa_data/pfx/myPdfSigningCert.pfx','secret');
  if (success = False) then
    begin
      WriteLn(cert.LastErrorText);
      Exit;
    end;

  //  Tell the pdf object to use the certificate for signing.
  success := pdf.SetSigningCert(cert);
  if (success = False) then
    begin
      WriteLn(pdf.LastErrorText);
      Exit;
    end;

  success := pdf.SignPdf(json,'qa_output/hello_signed.pdf');
  if (success = False) then
    begin
      WriteLn(pdf.LastErrorText);
      Exit;
    end;

  WriteLn('The PDF has been successfully cryptographically signed.');

  //  The appearance of the signature appears in Adobe Acrobat as shown here:

  //  (image:https://example-code.com/images/signature1.jpg/endImage)


  pdf.Free;
  json.Free;
  cert.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.