B4X 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. B4X

Dim success As Boolean = 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.
Dim cert As ChilkatCert
cert.Initialize("cert")
success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx", "secret")
If success = False Then
    Log(cert.LastErrorText)
    Return
End If


Dim pdf As ChilkatPdf
pdf.Initialize("pdf")
success = pdf.LoadFile("qa_data/pdf/two_page_memo.pdf")
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If


'  Encrypt with AES-256 and do not permit modifying.
pdf.UserPassword = "user-secret"
pdf.OwnerPassword = "owner-secret"
Dim json As ChilkatJsonObject
json.Initialize
json.UpdateBool("permissions.modify", False)
Dim jsonOut As ChilkatJsonObject
jsonOut.Initialize
success = pdf.Protection("encrypt", json, jsonOut)
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If


'  The encryption is still pending.  SignPdf applies it first and signs the encrypted result.
success = pdf.SetSigningCert(cert)
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If

Dim sigOpts As ChilkatJsonObject
sigOpts.Initialize
sigOpts.UpdateBool("invisibleSignature", True)
sigOpts.UpdateInt("signingCertificateV2", 1)
sigOpts.UpdateInt("signingTime", 1)
success = pdf.SignPdf(sigOpts, "qa_output/memo_encrypted_signed.pdf")
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If


'  The result is encrypted and signed.
Dim check As ChilkatPdf
check.Initialize("check")
check.UserPassword = "user-secret"
success = check.LoadFile("qa_output/memo_encrypted_signed.pdf")
If success = False Then
    Log(check.LastErrorText)
    Return
End If

Dim empty As ChilkatJsonObject
empty.Initialize
Dim info As ChilkatJsonObject
info.Initialize
success = check.Protection("getInfo", empty, info)
If success = False Then
    Log(check.LastErrorText)
    Return
End If

Log("algorithm: " & info.StringOf("loaded.algorithm"))
Log("signatures: " & check.NumSignatures)
Dim sigInfo As ChilkatJsonObject
sigInfo.Initialize
Dim verified As Boolean = check.VerifySignature(0, sigInfo)
Log("signature verifies: " & 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 = check.SetSigningCert(cert)
If success = False Then
    Log(check.LastErrorText)
    Return
End If

success = check.SignPdf(sigOpts, "qa_output/memo_signed_twice.pdf")
If success = False Then
    Log("A second signature was refused: the permissions do not allow it.")
End If


'  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.
Dim owner As ChilkatPdf
owner.Initialize("owner")
owner.UserPassword = "user-secret"
owner.OwnerPassword = "owner-secret"
success = owner.LoadFile("qa_output/memo_encrypted_signed.pdf")
If success = False Then
    Log(owner.LastErrorText)
    Return
End If

success = owner.SetSigningCert(cert)
If success = False Then
    Log(owner.LastErrorText)
    Return
End If

success = owner.SignPdf(sigOpts, "qa_output/memo_signed_twice.pdf")
If success = False Then
    Log(owner.LastErrorText)
    Return
End If


Dim twice As ChilkatPdf
twice.Initialize("twice")
twice.UserPassword = "user-secret"
success = twice.LoadFile("qa_output/memo_signed_twice.pdf")
If success = False Then
    Log(twice.LastErrorText)
    Return
End If

Log("signatures after signing with owner rights: " & twice.NumSignatures)
verified = twice.VerifySignature(0, sigInfo)
Log("first signature still verifies: " & verified)
verified = twice.VerifySignature(1, sigInfo)
Log("second signature verifies: " & 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