Swift 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. Swift

func chilkatTest() {
    var success: Bool = 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.
    let cert = CkoCert()!
    success = cert.loadPfxFile(path: "qa_data/pfx/myPdfSigningCert.pfx", password: "secret")
    if success == false {
        print("\(cert.lastErrorText!)")
        return
    }

    let pdf = CkoPdf()!
    success = pdf.loadFile(filePath: "qa_data/pdf/two_page_memo.pdf")
    if success == false {
        print("\(pdf.lastErrorText!)")
        return
    }

    //  Encrypt with AES-256 and do not permit modifying.
    pdf.userPassword = "user-secret"
    pdf.ownerPassword = "owner-secret"
    let json = CkoJsonObject()!
    json.updateBool(jsonPath: "permissions.modify", value: false)
    let jsonOut = CkoJsonObject()!
    success = pdf.protection(op: "encrypt", jsonIn: json, jsonOut: jsonOut)
    if success == false {
        print("\(pdf.lastErrorText!)")
        return
    }

    //  The encryption is still pending.  SignPdf applies it first and signs the encrypted result.
    success = pdf.setSigningCert(cert: cert)
    if success == false {
        print("\(pdf.lastErrorText!)")
        return
    }

    let sigOpts = CkoJsonObject()!
    sigOpts.updateBool(jsonPath: "invisibleSignature", value: true)
    sigOpts.updateInt(jsonPath: "signingCertificateV2", value: 1)
    sigOpts.updateInt(jsonPath: "signingTime", value: 1)
    success = pdf.sign(jsonOptions: sigOpts, outFilePath: "qa_output/memo_encrypted_signed.pdf")
    if success == false {
        print("\(pdf.lastErrorText!)")
        return
    }

    //  The result is encrypted and signed.
    let check = CkoPdf()!
    check.userPassword = "user-secret"
    success = check.loadFile(filePath: "qa_output/memo_encrypted_signed.pdf")
    if success == false {
        print("\(check.lastErrorText!)")
        return
    }

    let empty = CkoJsonObject()!
    let info = CkoJsonObject()!
    success = check.protection(op: "getInfo", jsonIn: empty, jsonOut: info)
    if success == false {
        print("\(check.lastErrorText!)")
        return
    }

    print("algorithm: \(info.string(of: "loaded.algorithm")!)")
    print("signatures: \(check.numSignatures.intValue)")
    let sigInfo = CkoJsonObject()!
    var verified: Bool = check.verifySignature(index: 0, sigInfo: sigInfo)
    print("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: cert)
    if success == false {
        print("\(check.lastErrorText!)")
        return
    }

    success = check.sign(jsonOptions: sigOpts, outFilePath: "qa_output/memo_signed_twice.pdf")
    if success == false {
        print("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.
    let owner = CkoPdf()!
    owner.userPassword = "user-secret"
    owner.ownerPassword = "owner-secret"
    success = owner.loadFile(filePath: "qa_output/memo_encrypted_signed.pdf")
    if success == false {
        print("\(owner.lastErrorText!)")
        return
    }

    success = owner.setSigningCert(cert: cert)
    if success == false {
        print("\(owner.lastErrorText!)")
        return
    }

    success = owner.sign(jsonOptions: sigOpts, outFilePath: "qa_output/memo_signed_twice.pdf")
    if success == false {
        print("\(owner.lastErrorText!)")
        return
    }

    let twice = CkoPdf()!
    twice.userPassword = "user-secret"
    success = twice.loadFile(filePath: "qa_output/memo_signed_twice.pdf")
    if success == false {
        print("\(twice.lastErrorText!)")
        return
    }

    print("signatures after signing with owner rights: \(twice.numSignatures.intValue)")
    verified = twice.verifySignature(index: 0, sigInfo: sigInfo)
    print("first signature still verifies: \(verified)")
    verified = twice.verifySignature(index: 1, sigInfo: sigInfo)
    print("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

}