Visual FoxPro

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.

Visual FoxPro

LOCAL lnSuccess
LOCAL loPdf
LOCAL loJson
LOCAL loCert

lnSuccess = 0

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

loPdf = CreateObject('Chilkat.Pdf')

*  Load a PDF to be signed.
*  The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
lnSuccess = loPdf.LoadFile("qa_data/pdf/hello.pdf")
IF (lnSuccess = 0) THEN
    ? loPdf.LastErrorText
    RELEASE loPdf
    CANCEL
ENDIF

*  Options for signing are specified in JSON.
loJson = CreateObject('Chilkat.JsonObject')

*  In most cases, the signingCertificateV2 and signingTime attributes are required.
loJson.UpdateInt("signingCertificateV2",1)
loJson.UpdateInt("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).
loJson.UpdateBool("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.
loPdf.UncommonOptions = "LOG_OCSP_HTTP,LOG_CRL_HTTP"

*  Define the appearance of the signature.
loJson.UpdateInt("page",1)
loJson.UpdateString("appearance.y","top")
loJson.UpdateString("appearance.x","left")
loJson.UpdateString("appearance.fontScale","10.0")
loJson.UpdateString("appearance.text[0]","Digitally signed by: cert_cn")
loJson.UpdateString("appearance.text[1]","current_dt")
loJson.UpdateString("appearance.text[2]","This is an LTV-enabled signature.")

*  Load the signing certificate. (Use your own certificate.)
loCert = CreateObject('Chilkat.Cert')
lnSuccess = loCert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","pfxPassword")
IF (lnSuccess = 0) THEN
    ? loCert.LastErrorText
    RELEASE loPdf
    RELEASE loJson
    RELEASE loCert
    CANCEL
ENDIF

*  Tell the pdf object to use the certificate for signing.
lnSuccess = loPdf.SetSigningCert(loCert)
IF (lnSuccess = 0) THEN
    ? loPdf.LastErrorText
    RELEASE loPdf
    RELEASE loJson
    RELEASE loCert
    CANCEL
ENDIF

lnSuccess = loPdf.SignPdf(loJson,"qa_output/hello_ltv_signed.pdf")
IF (lnSuccess = 0) THEN
    ? loPdf.LastErrorText
    RELEASE loPdf
    RELEASE loJson
    RELEASE loCert
    CANCEL
ENDIF

? "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)

RELEASE loPdf
RELEASE loJson
RELEASE loCert