Go Requires Chilkat v11.7.0+

Encrypt and Sign a PDF, and Sign an Encrypted PDF

See more PDF Protection Examples

Demonstrates signing together with encryption. A pending encrypt is applied by SignPdf before it signs, so one call produces a PDF that is both encrypted and signed. A PDF that is already encrypted can be signed too, and stays encrypted. When it was opened with only the user password its permissions decide: adding a signature field needs both the modify and the annotate permission. Loading the PDF with its owner password lifts that. Go

    success := false

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

    //  The PDF used in this example is available at two_page_memo.pdf

    //  The signing certificate, with its private key.
    cert := chilkat.NewCert()
    success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","secret")
    if success == false {
        fmt.Println(cert.LastErrorText())
        cert.DisposeCert()
        return
    }

    pdf := chilkat.NewPdf()
    success = pdf.LoadFile("qa_data/pdf/two_page_memo.pdf")
    if success == false {
        fmt.Println(pdf.LastErrorText())
        cert.DisposeCert()
        pdf.DisposePdf()
        return
    }

    //  Encrypt with AES-256 and do not permit modifying.
    pdf.SetUserPassword("user-secret")
    pdf.SetOwnerPassword("owner-secret")
    json := chilkat.NewJsonObject()
    json.UpdateBool("permissions.modify",false)
    jsonOut := chilkat.NewJsonObject()
    success = pdf.Protection("encrypt",json,jsonOut)
    if success == false {
        fmt.Println(pdf.LastErrorText())
        cert.DisposeCert()
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jsonOut.DisposeJsonObject()
        return
    }

    //  The encryption is still pending.  SignPdf applies it first and signs the encrypted result.
    success = pdf.SetSigningCert(cert)
    if success == false {
        fmt.Println(pdf.LastErrorText())
        cert.DisposeCert()
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jsonOut.DisposeJsonObject()
        return
    }

    sigOpts := chilkat.NewJsonObject()
    sigOpts.UpdateBool("invisibleSignature",true)
    sigOpts.UpdateInt("signingCertificateV2",1)
    sigOpts.UpdateInt("signingTime",1)
    success = pdf.SignPdf(sigOpts,"qa_output/memo_encrypted_signed.pdf")
    if success == false {
        fmt.Println(pdf.LastErrorText())
        cert.DisposeCert()
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jsonOut.DisposeJsonObject()
        sigOpts.DisposeJsonObject()
        return
    }

    //  The result is encrypted and signed.
    check := chilkat.NewPdf()
    check.SetUserPassword("user-secret")
    success = check.LoadFile("qa_output/memo_encrypted_signed.pdf")
    if success == false {
        fmt.Println(check.LastErrorText())
        cert.DisposeCert()
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jsonOut.DisposeJsonObject()
        sigOpts.DisposeJsonObject()
        check.DisposePdf()
        return
    }

    empty := chilkat.NewJsonObject()
    info := chilkat.NewJsonObject()
    success = check.Protection("getInfo",empty,info)
    if success == false {
        fmt.Println(check.LastErrorText())
        cert.DisposeCert()
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jsonOut.DisposeJsonObject()
        sigOpts.DisposeJsonObject()
        check.DisposePdf()
        empty.DisposeJsonObject()
        info.DisposeJsonObject()
        return
    }

    fmt.Println("algorithm: ", *info.StringOf("loaded.algorithm"))
    fmt.Println("signatures: ", check.NumSignatures())
    sigInfo := chilkat.NewJsonObject()
    verified := check.VerifySignature(0,sigInfo)
    fmt.Println("signature verifies: ", verified)

    //  Signing an encrypted PDF.  This one was opened with only the user password, and its
    //  permissions do not allow modifying, so another signature is refused.
    success = check.SetSigningCert(cert)
    if success == false {
        fmt.Println(check.LastErrorText())
        cert.DisposeCert()
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jsonOut.DisposeJsonObject()
        sigOpts.DisposeJsonObject()
        check.DisposePdf()
        empty.DisposeJsonObject()
        info.DisposeJsonObject()
        sigInfo.DisposeJsonObject()
        return
    }

    success = check.SignPdf(sigOpts,"qa_output/memo_signed_twice.pdf")
    if success == false {
        fmt.Println("A second signature was refused: the permissions do not allow it.")
    }

    //  Loaded with the owner password, the same PDF can be signed.  It stays encrypted, and the
    //  first signature stays valid because the new one is added as an incremental update.
    owner := chilkat.NewPdf()
    owner.SetUserPassword("user-secret")
    owner.SetOwnerPassword("owner-secret")
    success = owner.LoadFile("qa_output/memo_encrypted_signed.pdf")
    if success == false {
        fmt.Println(owner.LastErrorText())
        cert.DisposeCert()
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jsonOut.DisposeJsonObject()
        sigOpts.DisposeJsonObject()
        check.DisposePdf()
        empty.DisposeJsonObject()
        info.DisposeJsonObject()
        sigInfo.DisposeJsonObject()
        owner.DisposePdf()
        return
    }

    success = owner.SetSigningCert(cert)
    if success == false {
        fmt.Println(owner.LastErrorText())
        cert.DisposeCert()
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jsonOut.DisposeJsonObject()
        sigOpts.DisposeJsonObject()
        check.DisposePdf()
        empty.DisposeJsonObject()
        info.DisposeJsonObject()
        sigInfo.DisposeJsonObject()
        owner.DisposePdf()
        return
    }

    success = owner.SignPdf(sigOpts,"qa_output/memo_signed_twice.pdf")
    if success == false {
        fmt.Println(owner.LastErrorText())
        cert.DisposeCert()
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jsonOut.DisposeJsonObject()
        sigOpts.DisposeJsonObject()
        check.DisposePdf()
        empty.DisposeJsonObject()
        info.DisposeJsonObject()
        sigInfo.DisposeJsonObject()
        owner.DisposePdf()
        return
    }

    twice := chilkat.NewPdf()
    twice.SetUserPassword("user-secret")
    success = twice.LoadFile("qa_output/memo_signed_twice.pdf")
    if success == false {
        fmt.Println(twice.LastErrorText())
        cert.DisposeCert()
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jsonOut.DisposeJsonObject()
        sigOpts.DisposeJsonObject()
        check.DisposePdf()
        empty.DisposeJsonObject()
        info.DisposeJsonObject()
        sigInfo.DisposeJsonObject()
        owner.DisposePdf()
        twice.DisposePdf()
        return
    }

    fmt.Println("signatures after signing with owner rights: ", twice.NumSignatures())
    verified = twice.VerifySignature(0,sigInfo)
    fmt.Println("first signature still verifies: ", verified)
    verified = twice.VerifySignature(1,sigInfo)
    fmt.Println("second signature verifies: ", verified)

    //  Sample output:

    //  algorithm: aes-256
    //  signatures: 1
    //  signature verifies: True
    //  A second signature was refused: the permissions do not allow it.
    //  signatures after signing with owner rights: 2
    //  first signature still verifies: True
    //  second signature verifies: True

    cert.DisposeCert()
    pdf.DisposePdf()
    json.DisposeJsonObject()
    jsonOut.DisposeJsonObject()
    sigOpts.DisposeJsonObject()
    check.DisposePdf()
    empty.DisposeJsonObject()
    info.DisposeJsonObject()
    sigInfo.DisposeJsonObject()
    owner.DisposePdf()
    twice.DisposePdf()