(Go) Sign PDF with Timestamp from TSA (Timestamp Server Authority)

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This example demonstrates how to a sign a PDF that is both long-term validation (LTV) enabled and includes a validating timestamp from a TSA (Timestamp Server Authority).

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

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

    pdf := chilkat.NewPdf()

    // Load a PDF to be signed.
    // The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
    success := pdf.LoadFile("qa_data/pdf/hello.pdf")
    if success == false {
        fmt.Println(pdf.LastErrorText())
        pdf.DisposePdf()
        return
    }

    // Options for signing are specified in JSON.
    json := chilkat.NewJsonObject()

    // In most cases, the signingCertificateV2 and signingTime attributes are required.
    json.UpdateInt("signingCertificateV2",1)
    json.UpdateInt("signingTime",1)

    // Tell Chilkat to create an LTV-enabled (long term validation) signature.
    // See PDF Long-Term Validation (LTV) Signature Example for more detailed comments about "ltvOcsp".
    json.UpdateBool("ltvOcsp",true)

    // Tell Chilkat to request a timestamp from a TSA server and include the timestamp token (1.2.840.113549.1.9.16.2.14)
    // in the CMS signature's authentication attributes
    json.UpdateBool("timestampToken.enabled",true)

    // In this example, we'll use a free TSA server (timestamp.digicert.com), but you may want to use your own timestamp authority server.
    json.UpdateString("timestampToken.tsaUrl","http://timestamp.digicert.com")

    // If the timestamp server requires a username/password, do the following.  Otherwise omit the following few lines of code.
    json.UpdateString("timestampToken.tsaUsername","the_tsa_username")
    json.UpdateString("timestampToken.tsaPassword","the_tsa_password")

    // When requesting the timestamp token, ask the server to include its certificate in the timestamp token response.
    // This allows for the timestamp server's certificate to be included in the LTV validation (i.e. if the timestamp server
    // has an OCSP URL, then Chilkat will also do the OCSP request for the timestamp server's certificate.)
    json.UpdateBool("timestampToken.requestTsaCert",true)

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

    // Load the signing certificate. (Use your own certificate.)
    cert := chilkat.NewCert()
    success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","pfxPassword")
    if success == false {
        fmt.Println(cert.LastErrorText())
        pdf.DisposePdf()
        json.DisposeJsonObject()
        cert.DisposeCert()
        return
    }

    // Tell the pdf object to use the certificate for signing.
    success = pdf.SetSigningCert(cert)
    if success == false {
        fmt.Println(pdf.LastErrorText())
        pdf.DisposePdf()
        json.DisposeJsonObject()
        cert.DisposeCert()
        return
    }

    success = pdf.SignPdf(json,"qa_output/hello_ltv_signed_with_timestamp.pdf")
    if success == false {
        fmt.Println(pdf.LastErrorText())
        pdf.DisposePdf()
        json.DisposeJsonObject()
        cert.DisposeCert()
        return
    }

    fmt.Println("The PDF has been successfully cryptographically signed with TSA timestamp and long-term validation.")

    // If you open the Signature Panel in Adobe Acrobat, it will indicate that the signature is LTV enabled
    // and contains an embedded timestamp:
    

    pdf.DisposePdf()
    json.DisposeJsonObject()
    cert.DisposeCert()