Delphi DLL Requires Chilkat v11.7.0+

Encrypt and Sign a PDF, and Sign an Encrypted PDF

See more PDF Protection Examples

Demonstrates signing together with encryption. A pending encrypt is applied by SignPdf before it signs, so one call produces a PDF that is both encrypted and signed. A PDF that is already encrypted can be signed too, and stays encrypted. When it was opened with only the user password its permissions decide: adding a signature field needs both the modify and the annotate permission. Loading the PDF with its owner password lifts that. Delphi DLL

var
success: Boolean;
cert: HCkCert;
pdf: HCkPdf;
json: HCkJsonObject;
jsonOut: HCkJsonObject;
sigOpts: HCkJsonObject;
check: HCkPdf;
empty: HCkJsonObject;
info: HCkJsonObject;
sigInfo: HCkJsonObject;
verified: Boolean;
owner: HCkPdf;
twice: HCkPdf;

begin
success := False;

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

//  The PDF used in this example is available at two_page_memo.pdf

//  The signing certificate, with its private key.
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;

pdf := CkPdf_Create();
success := CkPdf_LoadFile(pdf,'qa_data/pdf/two_page_memo.pdf');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(pdf));
    Exit;
  end;

//  Encrypt with AES-256 and do not permit modifying.
CkPdf_putUserPassword(pdf,'user-secret');
CkPdf_putOwnerPassword(pdf,'owner-secret');
json := CkJsonObject_Create();
CkJsonObject_UpdateBool(json,'permissions.modify',False);
jsonOut := CkJsonObject_Create();
success := CkPdf_Protection(pdf,'encrypt',json,jsonOut);
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(pdf));
    Exit;
  end;

//  The encryption is still pending.  SignPdf applies it first and signs the encrypted result.
success := CkPdf_SetSigningCert(pdf,cert);
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(pdf));
    Exit;
  end;
sigOpts := CkJsonObject_Create();
CkJsonObject_UpdateBool(sigOpts,'invisibleSignature',True);
CkJsonObject_UpdateInt(sigOpts,'signingCertificateV2',1);
CkJsonObject_UpdateInt(sigOpts,'signingTime',1);
success := CkPdf_SignPdf(pdf,sigOpts,'qa_output/memo_encrypted_signed.pdf');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(pdf));
    Exit;
  end;

//  The result is encrypted and signed.
check := CkPdf_Create();
CkPdf_putUserPassword(check,'user-secret');
success := CkPdf_LoadFile(check,'qa_output/memo_encrypted_signed.pdf');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(check));
    Exit;
  end;
empty := CkJsonObject_Create();
info := CkJsonObject_Create();
success := CkPdf_Protection(check,'getInfo',empty,info);
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(check));
    Exit;
  end;
Memo1.Lines.Add('algorithm: ' + CkJsonObject__stringOf(info,'loaded.algorithm'));
Memo1.Lines.Add('signatures: ' + IntToStr(CkPdf_getNumSignatures(check)));
sigInfo := CkJsonObject_Create();
verified := CkPdf_VerifySignature(check,0,sigInfo);
Memo1.Lines.Add('signature verifies: ' + IntToStr(Ord(verified)));

//  Signing an encrypted PDF.  This one was opened with only the user password, and its
//  permissions do not allow modifying, so another signature is refused.
success := CkPdf_SetSigningCert(check,cert);
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(check));
    Exit;
  end;
success := CkPdf_SignPdf(check,sigOpts,'qa_output/memo_signed_twice.pdf');
if (success = False) then
  begin
    Memo1.Lines.Add('A second signature was refused: the permissions do not allow it.');
  end;

//  Loaded with the owner password, the same PDF can be signed.  It stays encrypted, and the
//  first signature stays valid because the new one is added as an incremental update.
owner := CkPdf_Create();
CkPdf_putUserPassword(owner,'user-secret');
CkPdf_putOwnerPassword(owner,'owner-secret');
success := CkPdf_LoadFile(owner,'qa_output/memo_encrypted_signed.pdf');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(owner));
    Exit;
  end;
success := CkPdf_SetSigningCert(owner,cert);
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(owner));
    Exit;
  end;
success := CkPdf_SignPdf(owner,sigOpts,'qa_output/memo_signed_twice.pdf');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(owner));
    Exit;
  end;

twice := CkPdf_Create();
CkPdf_putUserPassword(twice,'user-secret');
success := CkPdf_LoadFile(twice,'qa_output/memo_signed_twice.pdf');
if (success = False) then
  begin
    Memo1.Lines.Add(CkPdf__lastErrorText(twice));
    Exit;
  end;
Memo1.Lines.Add('signatures after signing with owner rights: ' + IntToStr(CkPdf_getNumSignatures(twice)));
verified := CkPdf_VerifySignature(twice,0,sigInfo);
Memo1.Lines.Add('first signature still verifies: ' + IntToStr(Ord(verified)));
verified := CkPdf_VerifySignature(twice,1,sigInfo);
Memo1.Lines.Add('second signature verifies: ' + IntToStr(Ord(verified)));

//  Sample output:

//  algorithm: aes-256
//  signatures: 1
//  signature verifies: True
//  A second signature was refused: the permissions do not allow it.
//  signatures after signing with owner rights: 2
//  first signature still verifies: True
//  second signature verifies: True

CkCert_Dispose(cert);
CkPdf_Dispose(pdf);
CkJsonObject_Dispose(json);
CkJsonObject_Dispose(jsonOut);
CkJsonObject_Dispose(sigOpts);
CkPdf_Dispose(check);
CkJsonObject_Dispose(empty);
CkJsonObject_Dispose(info);
CkJsonObject_Dispose(sigInfo);
CkPdf_Dispose(owner);
CkPdf_Dispose(twice);