Let's say we receive a PDF document that is alredy signed.
We'd like to add a new signature field to the document and send it to the person that needs to sign it inside our environment.
We've seen that it's possible with AcrobatPro to directly sign the document, but it's not possible to just add the signature field to the document without signing it. We don't have AcrobatPro licenses for every user on the organization that have to sign external documents, so we're looking for a way to prepare the document for them, so they can sign it just within Acrobat Reader.
We are on a quite big organization (around 3000 ppl) and our ERP already manages everything related to signatures to our own documentation, but we are seeking for a solution to sign external documents that already have been externally signed while our provider evolves a solution inside the ERP.
Related
I send the document to DocuSign in draft status. Then user(contract owner) logs into DocuSign, adds additional signers and tags then sends the document for signing.
Is it possible to get the original unsigned document(pdf) that was sent after the document is completed via the API?
The reason I need the original document is to make sure that the user(contract owner) has not changed/modified the document in DocuSign.
I want to make sure the signed document is exactly the one I sent via API.
DocuSign does not have granular permissions to block changes to the documents when the Envelope is in draft status.
Re: Is there a way to get back the original unsigned document that was sent to DocuSign after it is signed/completed?
Answer: unfortunately, no. As soon as original documents are uploaded to DocuSign, they are converted into a "flat" (no logic) PDF. The original document is then discarded.
As a workaround, you could programmatically create a template, then create an envelope from the template. Then the user could tag the document without the ability to change the document. See use case 8, creating a template programmatically for code examples. These are on the eg-03 series of examples. Eg, the PHP code example.
Or better, update your application to tag the documents for the user.
We are investigating the idea of enabling the documents in an envelope to be locked. Please ask your DocuSign business or support contact to add your company information to DocuSign internal issue number SMPI-236.
Use case: My system needs to retrieve authorization forms from a variety of sources. There is no standard form - each source may define their own authorization form, but each authorization form requires exactly one signature. None of the blank forms will have PDF signature field markup - they will just be simple PDFs originally meant for printing and wet signing. For example, every summer camp in the country has their own release form. My system will receive those forms and present them for signature, without knowing what the form looks like ahead of time.
This means I will not have the chance to mark up the form with DocuSign "Sign Here" boxes.
Is it possible in DocuSign to have a system send in a form and allow the signer to manually determine exactly where they want to place their signature? Without giving the signer duties such as preparing the document themselves - I just want them to see the form on screen, and be prompted to "Click wherever you think you should sign", just like they would do in the paper world.
You can use DocuSign free form signing for your usecase.
See this DocuSign Blog Post for more information.
Free-form signing occurs when no tags are placed on a document submitted via DocuSign. This means that the signer will be presented with a palette of signature options (Signature, Initial, Full Name, etc.) which can be applied to the document at will.
First of all, a bit of background - the actual questions are at the bottom.
I'm currently working on a web-based app (sort of SaaS) which allows users to send forms to their own customers.
These forms are simple, small contracts for small jobs where their customers say "Yeah sure, I'll do this and here's my confirmation".
The sort of thing that is being "signed" does not require a fully qualified digital signature and an electronic signature will suffice.
While, in this case, a simple checkbox saying "Yeah, I'll do this" would legally be sufficient, I'm keen to implement it with a signature pad. To be honest, it's just for the factor of being seemingly more binding and, well, "neat".
The current workflow looks like this:
User's customer opens web-form (the party being asked to sign is the only person in the universe to know the direct link)
Ticks a few boxes and enters text
Clicks "Sign" which opens an HTML5 signature pad (mobile) or a simple input (PC) to type their name
Clicks "Accept"
A PDF is generated for download and stored on the server (along with timestamp, IP, and a couple of other bits of information)
As you can see, the agreement in its entirety constitutes a simple electronic signature - even without the bells and whistles.
What I would like to do
As with any simple electronic signature, it's easy for any party to say that a document may have been tampered with.
So what I did is properly sign the PDF according to the specifications (using tcpdf): that entailed first generating the PDF and then adding the signature to the /Sig dictionary, then generating a digest across all byte-ranges (excluding the signature), linking it up with a .crt file and voilá: the document is signed with the lovely benefit of the signature becoming invalid if even a single byte is changed.
Now to the questions:
Is it possible to benefit from the "tamper-validation" without using a certificate? Like I say, these are not supposed to be digital signatures but rather simple, electronic signatures. Still, I'd like to benefit from any post-signature changes being highlighted.
Alternatively, I could also simply use a proper certificate for the signing process. But this certificate would be mine rather than my users' or even my users' customers'. In that sense, would it do more harm than good? I.e. the certificate belongs to the wrong party and therefore becomes meaningless; I, rather than the signatory vouches; "The document was changed and re-signed after I signed"; etc.
Is it possible to benefit from the "tamper-validation" without using a certificate? Like I say, these are not supposed to be digital signatures but rather simple, electronic signatures. Still, I'd like to benefit from any post-signature changes being highlighted.
No, at least as long as you want to do this in an interoperable way.
You can of course invent your own security system, create a PDF viewer or at least plugins for the commonly used PDF viewers to support your system, and roll these programs out to your users.
But if you want existing Adobe Reader as-is to verify the signature, you've got to go the X509 PKI way.
Alternatively, I could also simply use a proper certificate for the signing process. But this certificate would be mine rather than my users' or even my users' customers'. In that sense, would it do more harm than good? I.e. the certificate belongs to the wrong party and therefore becomes meaningless; I, rather than the signatory vouches; "The document was changed and re-signed after I signed"; etc.
When using your own certificate for signing, don't forget to properly fill the reason field so it indicates that your signature is applied as a counter signature to guarantee validatability.
With that in place I don't see your signature doing any harm.
The question is how much good it does, though.
Obviously the user still can claim that he signed something different... because he did! He signed the web form, not the PDF. Thus, you might have to provide proof that the PDF reflects exactly what the web form showed anyways, that the user signed something equivalent.
If you want actual non-repudiation by the user, you need to make him sign personally in a manner that is commonly accepted to not allow tampering. In other words, your user needs to apply proper digital signatures himself. Everything else is open to claims of forgery.
You can use trusted time-stamp (defined in RFC3161) instead of signature created by the customer or by your server. Time-stamp protects document integrity and proves that your document existed before a particular time. Technically speaking it is a digital signature created by a trusted 3rd party.
Context
My overall goal is to make a set of PDFs available, in such a way that users can be assured of the provenance of the documents (i.e., they came from the origin that they are expected to come from). I'm thinking about doing this by digitally signing the PDFs on the server. These signatures won't be in risk of expiring, because the server can just reissue new signed PDFs when the certificate is updated. Using SSL to serve the documents wouldn't be enough, because the files can be passed on to third parties, who don't want/need to access the server.
Problem
The expiration issue arises because some of these PDFs will already have one or more digital signatures (e.g., created for legal purposes). My question is, if the server signs the PDFs, will it also be ensuring the continued validity of the previous signatures, even after they expire, as long as the latest signature is valid?
I'm asking more on the theoretical side, although I plan to implement what I describe using iText, so any pointers on how to use it for my purpose are also welcome.
No, in a PDF all signatures should be validated independently. If you open a PDF with multiple signatures In Adbobe Reader all signatures are validated and you are going to get a warning message if one of the signature validations fails.
If you want to prevent against signature validation issues (for instance a validation failure due to signing certificate expiration) you should look at the PAdES standard (PDF Advanced Electronic Signature) Part #4 (PAdES-LTV Profile - PAdES Long Term Validation). This section of the standard deals with maintaining a proof of the validation across time in order to be able to revalidate the signatures in the future.
I don't know iText very much but it seems that PAdES-LTV is supported since I found this code sample : How to apply verification according to PAdES-LTV
Immagine a web application that lets you digitally sign (with personal digital certificates pkcs12 released by trusted CAs) and timestamp PDF documents with a Java applet or Active X. This must obviously happen on the machine of the user because the private key of the certificate is stored locally.
So once the PDF is signed and timestamped it is uploaded on the server.
Does the uploaded file have the same features of the one created locally? Does it have sense to talk about "the original version of the file"?
I'm a bit confused on this.
Correction:
i mean digitally sign a document with the private key of a personal digital certificate (should be pkcs7, pkcs12) to ensure that it has really been signed by someone and not someone else.
If by "the original version of the file" you mean that you intend to "freeze" the document so that nobody can ever make changes to it again - that is neither possible nor the purpose of a digital signature. Anyone could simply "cut out" the a signature embedded within a document, nobody would notice.
Protecting a document from subsequent modification involves some kind of DRM mechanism. For example, "watermarking" involving steganography is used to protect photos so that noone should be able to claim ownership of a photo, even after having modified it. But the technology is not very advanced yet, most algorithms can be easily broken.
This implies that the notion of "the original version of the file" in let's say a legal dispute is something that the involved parties have to agree upon in consent. There's no way to prove origin without either consent or a trusted third party that will attest the integrity of a document, e.g. if they have an independent copy of the document.
Apart from that, uploading a file should not change its contents. The file will have the exact same properties than the local one including the signature that was added on the client side.
The signature will only attest authenticity and integrity of the document. If it is vital for your application to be able to tell that the signed document received is actually the one that was expected, then I'd advise you to do the following:
Create the PDF on the server
Create a hash of the document (same algorithm that will be used by the signature applet)
Send the PDF to the client
Let the client sign it and send it back
Compare the client's hash with the one previously computed on the server
Validate the signature
Validating the signature will ensure integrity and authenticity, comparing the hashes will guarantee you that the signed document you received on the server is indeed a signed version of the original document previously created.
Concerning timestamps using local clocks: they're worthless, it's very easy to cheat. What you actually should use there is RFC 3161-compliant cryptographically secured timestamps, issued by a trusted third party. Currently that's the only reliable way to include the notion of time in PDF signatures. There's also built-in support for this in Adobe Reader for example. As these services are generally not available for free, it would make sense to add such a timestamp on the server after receiving the signed document. They are added as an unsigned attribute to the CMS (Adobe still speaks of PKCS7) signature, so it won't break the signature and can safely be added after signature creation.
Okay, let's try to answer your question (as I understand it).
You have some software which uses some private key (and a clock) to add a signature to a file.
This signature is depending on the contents of the file, and thus makes sure that the signer knew (or could have known) the contents of the file at the time it signed it. (There are some ways to have "blind signatures", but I assume this is not the case here.)
Uploading the signed file anywhere does not change anything here.
About the timestamp: The key holder can put in any timestamp it wants - so this only helps if you want to prove knowledge of the document at some point in time against the key holder, not if you are the key holder and want to prove that you signed at some point in time and not earlier or later. (Also, are you sure his clock is not skewed?)
About whether this is legally relevant, you will have to ask your lawyer. It might depend on
the jurisdiction in which the signature happened, and the one in which you want the signed document to be valid
whether the owner of the key had a chance to actually read the document before signing
whether the owner of the key had actually a choice of signing or not.
If you use some applet or ActiveX control in the user's browser, I would not be totally sure that the last two points really hold.