Delphi DLL

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. Delphi DLL

var
success: Boolean;
pdf: HCkPdf;
json: HCkJsonObject;
cert: HCkCert;

begin
success := False;

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

pdf := CkPdf_Create();

//  Load a PDF to be signed.
//  The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
success := CkPdf_LoadFile(pdf,'qa_data/pdf/hello.pdf');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(pdf));
    Exit;
  end;

//  Options for signing are specified in JSON.
json := CkJsonObject_Create();

//  In most cases, the signingCertificateV2 attribute is needed.
CkJsonObject_UpdateInt(json,'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.)
CkJsonObject_UpdateString(json,'hashAlgorithm','sha256');

//  To choose PKCSV1_5:
CkJsonObject_UpdateString(json,'signingAlgorithm','pkcs');
//  Alternatively, to choose RSASSA-PSS:
CkJsonObject_UpdateString(json,'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
CkJsonObject_UpdateInt(json,'page',1);
CkJsonObject_UpdateString(json,'appearance.y','top');
CkJsonObject_UpdateString(json,'appearance.x','left');

//  Use a font scale of 10.0
CkJsonObject_UpdateString(json,'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.
CkJsonObject_UpdateString(json,'appearance.text[0]','Digitally signed by: cert_cn');
CkJsonObject_UpdateString(json,'appearance.text[1]','current_dt');
CkJsonObject_UpdateString(json,'appearance.text[2]','The crazy brown fox jumps over the lazy dog.');

//  Load the signing certificate. (Use your own certificate.)
cert := CkCert_Create();
success := CkCert_LoadPfxFile(cert,'qa_data/pfx/myPdfSigningCert.pfx','secret');
if (success = False) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

//  Tell the pdf object to use the certificate for signing.
success := CkPdf_SetSigningCert(pdf,cert);
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(pdf));
    Exit;
  end;

success := CkPdf_SignPdf(pdf,json,'qa_output/hello_signed.pdf');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(pdf));
    Exit;
  end;

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

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

//  

CkPdf_Dispose(pdf);
CkJsonObject_Dispose(json);
CkCert_Dispose(cert);