(Delphi ActiveX) 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.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
pdf: TChilkatPdf;
success: Integer;
json: TChilkatJsonObject;
cert: TChilkatCert;

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

pdf := TChilkatPdf.Create(Self);

// 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 = 0) then
  begin
    Memo1.Lines.Add(pdf.LastErrorText);
    Exit;
  end;

// Options for signing are specified in JSON.
json := TChilkatJsonObject.Create(Self);

// 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 := TChilkatCert.Create(Self);
success := cert.LoadPfxFile('qa_data/pfx/myPdfSigningCert.pfx','secret');
if (success = 0) then
  begin
    Memo1.Lines.Add(cert.LastErrorText);
    Exit;
  end;

// Tell the pdf object to use the certificate for signing.
success := pdf.SetSigningCert(cert.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(pdf.LastErrorText);
    Exit;
  end;

success := pdf.SignPdf(json.ControlInterface,'qa_output/hello_signed.pdf');
if (success = 0) then
  begin
    Memo1.Lines.Add(pdf.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('The PDF has been successfully cryptographically signed.');

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


end;