PowerBuilder

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. PowerBuilder

integer li_rc
integer li_Success
oleobject loo_Pdf
oleobject loo_Json
oleobject loo_Cert

li_Success = 0

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

loo_Pdf = create oleobject
li_rc = loo_Pdf.ConnectToNewObject("Chilkat.Pdf")
if li_rc < 0 then
    destroy loo_Pdf
    MessageBox("Error","Connecting to COM object failed")
    return
end if

// Load a PDF to be signed.
// The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
li_Success = loo_Pdf.LoadFile("qa_data/pdf/hello.pdf")
if li_Success = 0 then
    Write-Debug loo_Pdf.LastErrorText
    destroy loo_Pdf
    return
end if

// Options for signing are specified in JSON.
loo_Json = create oleobject
li_rc = loo_Json.ConnectToNewObject("Chilkat.JsonObject")

// In most cases, the signingCertificateV2 attribute is needed.
loo_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.)
loo_Json.UpdateString("hashAlgorithm","sha256")

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

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

// Load the signing certificate. (Use your own certificate.)
loo_Cert = create oleobject
li_rc = loo_Cert.ConnectToNewObject("Chilkat.Cert")

li_Success = loo_Cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","secret")
if li_Success = 0 then
    Write-Debug loo_Cert.LastErrorText
    destroy loo_Pdf
    destroy loo_Json
    destroy loo_Cert
    return
end if

// Tell the pdf object to use the certificate for signing.
li_Success = loo_Pdf.SetSigningCert(loo_Cert)
if li_Success = 0 then
    Write-Debug loo_Pdf.LastErrorText
    destroy loo_Pdf
    destroy loo_Json
    destroy loo_Cert
    return
end if

li_Success = loo_Pdf.SignPdf(loo_Json,"qa_output/hello_signed.pdf")
if li_Success = 0 then
    Write-Debug loo_Pdf.LastErrorText
    destroy loo_Pdf
    destroy loo_Json
    destroy loo_Cert
    return
end if

Write-Debug "The PDF has been successfully cryptographically signed."

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

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


destroy loo_Pdf
destroy loo_Json
destroy loo_Cert