Tcl

Sign PDF with Long-Term Validation (LTV Enabled)

See more PDF Signatures Examples

This example demonstrates how to a sign a PDF with long-term validation (LTV) enabled.

Note: This example requires Chilkat v9.5.0.85 or greater.

Tcl

load ./chilkat.dll

set success 0

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

set pdf [new_CkPdf]

# Load a PDF to be signed.
# The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
set success [CkPdf_LoadFile $pdf "qa_data/pdf/hello.pdf"]
if {$success == 0} then {
    puts [CkPdf_lastErrorText $pdf]
    delete_CkPdf $pdf
    exit
}

# Options for signing are specified in JSON.
set json [new_CkJsonObject]

# In most cases, the signingCertificateV2 and signingTime attributes are required.
CkJsonObject_UpdateInt $json "signingCertificateV2" 1
CkJsonObject_UpdateInt $json "signingTime" 1

# Add the "ltvOcsp" instruction to the JSON passed to SignPdf.
# This is what causes Chilkat to create an LTV-enabled signature.
# 
# If we are signing a PDF that already has signatures, then the existing signatures
# are automatically verified, and Chilkat will do OCSP certificate status checking (if possible) 
# for those certs in existing signatures (including certs in the certificate chains) 
# that do not yet have a valid OCSP response in the DSS (Document Security Store).
# Chilkat will add the OCSP responses to the /OCSPs in the Document Security Store (/DSS).
# Also, and certificates from existing signatures not yet in the DSS are added to the /Certs 
# in the DSS.
# 
# Also, the "ltvOcsp" causes Chilkat to add the pdfRevocationInfoArchival authenticated attribute
# to the CMS signature.  The pdfRevocationInfoArchival attribute (1.2.840.113583.1.1.8)
# contains OCSP responses and the CRL for the issuer of the signing certificate.
# Therefore, Chilkat will send an OCSP request to the signing certificate's OCSP URl (if one exists)
# and will download the CRL from the issuer certificate's CRL Distribution Point (if one exists).
CkJsonObject_UpdateBool $json "ltvOcsp" 1

# -----------------------------------------------------------------------------------
# Note: If Chilkat produces a signed PDF, but the signature is not LTV-enabled,
# the cause might be related to a failure to download CRL's or OCSP requests.
# See Possible Solution for Failure to Produce LTV-enabled PDF Signature
# -----------------------------------------------------------------------------------
# You can add the following to UncommonOptions to get detailed information about the CRL and OCSP requests
# You shouldn't set the following logging options unless there is a need, because it adds a large amount of information to the LastErrorText.
CkPdf_put_UncommonOptions $pdf "LOG_OCSP_HTTP,LOG_CRL_HTTP"

# Define the appearance of the signature.
CkJsonObject_UpdateInt $json "page" 1
CkJsonObject_UpdateString $json "appearance.y" "top"
CkJsonObject_UpdateString $json "appearance.x" "left"
CkJsonObject_UpdateString $json "appearance.fontScale" "10.0"
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]" "This is an LTV-enabled signature."

# Load the signing certificate. (Use your own certificate.)
set cert [new_CkCert]

set success [CkCert_LoadPfxFile $cert "qa_data/pfx/myPdfSigningCert.pfx" "pfxPassword"]
if {$success == 0} then {
    puts [CkCert_lastErrorText $cert]
    delete_CkPdf $pdf
    delete_CkJsonObject $json
    delete_CkCert $cert
    exit
}

# Tell the pdf object to use the certificate for signing.
set success [CkPdf_SetSigningCert $pdf $cert]
if {$success == 0} then {
    puts [CkPdf_lastErrorText $pdf]
    delete_CkPdf $pdf
    delete_CkJsonObject $json
    delete_CkCert $cert
    exit
}

set success [CkPdf_SignPdf $pdf $json "qa_output/hello_ltv_signed.pdf"]
if {$success == 0} then {
    puts [CkPdf_lastErrorText $pdf]
    delete_CkPdf $pdf
    delete_CkJsonObject $json
    delete_CkCert $cert
    exit
}

puts "The PDF has been successfully cryptographically signed with long-term validation."

# If you open the Signature Panel in Adobe Acrobat, it will indicate that the signature is LTV enabled
# as shown here:
# (image:https://example-code.com/images/ltv_signature.jpg/endImage)

delete_CkPdf $pdf
delete_CkJsonObject $json
delete_CkCert $cert