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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. AutoIt

Local $bSuccess = False

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

$oPdf = ObjCreate("Chilkat.Pdf")

; Load a PDF to be signed.
; The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
$bSuccess = $oPdf.LoadFile("qa_data/pdf/hello.pdf")
If ($bSuccess = False) Then
    ConsoleWrite($oPdf.LastErrorText & @CRLF)
    Exit
EndIf

; Options for signing are specified in JSON.
$oJson = ObjCreate("Chilkat.JsonObject")

; In most cases, the signingCertificateV2 attribute is needed.
$oJson.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.)
$oJson.UpdateString("hashAlgorithm","sha256")

; To choose PKCSV1_5:
$oJson.UpdateString("signingAlgorithm","pkcs")
; Alternatively, to choose RSASSA-PSS:
$oJson.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
$oJson.UpdateInt("page",1)
$oJson.UpdateString("appearance.y","top")
$oJson.UpdateString("appearance.x","left")

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

; Load the signing certificate. (Use your own certificate.)
$oCert = ObjCreate("Chilkat.Cert")
$bSuccess = $oCert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","secret")
If ($bSuccess = False) Then
    ConsoleWrite($oCert.LastErrorText & @CRLF)
    Exit
EndIf

; Tell the pdf object to use the certificate for signing.
$bSuccess = $oPdf.SetSigningCert($oCert)
If ($bSuccess = False) Then
    ConsoleWrite($oPdf.LastErrorText & @CRLF)
    Exit
EndIf

$bSuccess = $oPdf.SignPdf($oJson,"qa_output/hello_signed.pdf")
If ($bSuccess = False) Then
    ConsoleWrite($oPdf.LastErrorText & @CRLF)
    Exit
EndIf

ConsoleWrite("The PDF has been successfully cryptographically signed." & @CRLF)

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

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