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Show HN: FalsiScan – Make it look like a PDF has been hand signed and scanned

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Re: Show HN: FalsiScan – Make it look like a PDF has been hand signed and scanned

#151

Post by mr_toad »

mikehollinger wrote: post #9

Mac’s pdf viewer Preview has a signature capture feature built in that’s pretty slick. I use it all the time and haven’t encountered an objection. Tbh I’d wonder why you need to fuzz up and fake scan the image. If someone’s requiring that the doc be “signed in ink” or some such, more power to you!

The reification of signatures and paper documents has to stop.

I can set up Apple Pay and use it across devices to make payments worth tens of thousands, but I can’t use the same technology to authenticate a document.

It really boils the blood.

Re: Show HN: FalsiScan – Make it look like a PDF has been hand signed and scanned

#152

Post by Ayesh »

spapas82 wrote: post #90

In my organization we have a different problem. We heavily use signed pdf files for all our internal documents - if a document is not signed it's not valid (they are mainly signed with JSignPdf). A number of internal applications need such signed files in order to proceed with a workflow. Checking if a PDF file has been digitally signed, how many signatures are there and if the signatures are all valid is not an easy…

This is cool, thanks for sharing.

Parsing a PDF file is in that list that nobody wants to write themselves. Next to writing a YAML parser.

Re: Show HN: FalsiScan – Make it look like a PDF has been hand signed and scanned

#153

Post by dror »

aclimatt wrote: post #71

Ha! My co-worker made one of these for the same reason. Some places still require "wet" signatures, and some people (us) like to stick it to bureaucracy and prove that they can't tell the difference. For a one-liner, if you use any tool to generate a realistic version of your signature, or do what I do and actually scan a version of your signature once, and then have that as a PNG that you can drop on any PDF of your…

Or just use Libreoffice and insert the image in the right place. Has worked for years.

Re: Show HN: FalsiScan – Make it look like a PDF has been hand signed and scanned

#154

Post by mr_toad »

mannykannot wrote: post #26
arkanciscan wrote: post #20

Earlier quoted context omitted.

But what if you aren't the one who forged your own signature? How are you going to prove that someone else scribbled something on a PDF?

The forging of a signature has always been a possibility, which is why witnesses are required for the important stuff. On the other hand, you would be right in thinking that there is a somewhat anachronistic element of theater in having signatures on electronic documents.

> The forging of a signature has always been a possibility

Yes, but it used to be difficult. If you can lift an image off one piece of paper and print it on another it becomes easy.

It’s no different than paper currency. If it’s easy to forge, then the real money becomes worthless.

Re: Show HN: FalsiScan – Make it look like a PDF has been hand signed and scanned

#155

Post by mr_toad »

DeathArrow wrote: post #93

I could use a mobile app to do that. In my country, to leave your home to do shopping in this period, you are required by military ordnance to fill a form stating the reason of leaving your home. You can show it on your mobile phone, but you have to print it, sign by hand and take a picture of it.

What if you don’t have a working printer at home? Do they just let you starve?

Re: Show HN: FalsiScan – Make it look like a PDF has been hand signed and scanned

#156

Post by CamperBob2 »

fastball wrote: post #150
CamperBob2 wrote: post #147

Earlier quoted context omitted.

The ones with political power are. It is exceedingly naive to claim otherwise. Google the term "Dominionism."

Dominionism is not a clearly defined practice/group/sect/etc. The most inclusive definition is basically just "people with strong beliefs want to run the democracy they live in according to those beliefs", which doesn't seem like a surprising way for anyone to behave. Yet, take even the most expansive and uncharitable definition, and still "dominionism" =/= "the end times are at hand and there are signs everywhere of…

You're lecturing to someone who grew up around these people, and who, paradoxically, has only watched their influence grow over the last thirty years.

So, yeah, thanks for that.

Re: Show HN: FalsiScan – Make it look like a PDF has been hand signed and scanned

#157

Post by sterlind »

zelly wrote: post #89
turbinerneiter wrote: post #6

I don't get the magical power of a signature at all. Everybody can write my name under a document. This project basically allows you to forge your own signature. Is it still legally binding? Do these rules even remember the original intent?

Signatures being meaningful is a downright American tradition. The country was founded based on signatures. It is never going away. Crytographic protocols can be added to verify signing, but until every civilian practices perfect opsec (never gonna happen), in-person signatures in front of a notary will always be the way business is done. Better technology (this program, Photoshop, deepfakes, quantum prime factorizat…

Post-quantum digital signature algorithms based on lattices are starting to get secure, efficient and based on simple mathematical constructs.

IIRC, the basic construction is you generate a lattice trapdoor matrix R, such that A*(Rt + e) ~= t. Finding an input p with small coefficients, for some t such that Ap = t reduces to one of lattice reduction problems, since it requires a finding "good" basis for the lattice (if you invert A you'll have huge coefficients, so you can't forge it. Having the trapdoor R to make p = Rt + e lets you use the trapdoor to find the preimage, and the gaussian vector e smudges it so that an attacker can't collect signatures to decipher R (this is learning with errors, another problem that reduces to lattice basis.) So the signature is easy to verify, and the trapdoor matrix is relatively small and efficient to compute (iirc a couple megs and Disclaimer: not a cryptographer, just a hobbyist.

Re: Show HN: FalsiScan – Make it look like a PDF has been hand signed and scanned

#158

Post by bambax »

I usually do the same thing, manually. I have a set of about 10 signatures that I vectorized (so that they scale with no visible artifacts). I apply one of those signatures to the PDF documents in an editor that can edit PDFs (currently using Affinity Designer or Publisher, they're excellent).

Then I take pride in outputting the cleaniest PDF possible. Never received any complaint. Most people on the receiving end probably print them out, and they appreciate the clean result, compared to what you get when you re-scan it (or intentionally blur it).

That said, for 27 pages (!!) that tool would prove a lifesaver.

Re: Show HN: FalsiScan – Make it look like a PDF has been hand signed and scanned

#159

Post by PeterisP »

shinryuu wrote: post #10
turbinerneiter wrote: post #6

I don't get the magical power of a signature at all. Everybody can write my name under a document. This project basically allows you to forge your own signature. Is it still legally binding? Do these rules even remember the original intent?

The question is, can you forge your own signature? If both parties agree that the document is legally binding it seems a bit unlikely that the document would fall under the forged label. Though I am not a lawyer. It's also worth noting that digital signatures throughout the european union have legal status.

You seem to be conflating the two different, incompatible meanings of "digital signatures" here.

This article is about digital signatures as in digital pictures of a signature. There's some support of them in, for example, some PDF tools. These do not have a legal status in EU.

And there are "digital signatures" as in cryptographic digital verification of documents using private/public key cryptography. This is the type of digital signatures for which EU has a legal status, and in many countries a support for verifying identity - for example, I can cryptographically sign documents using the chip on my gov't ID card, and if I receive such a document, then I can securely verify the identity of the signer without needing any preexisting relationship with them. But this has nothing to do with the pictures of signatures that this article is talking about, that seems to be more like a USA thing.

Re: Show HN: FalsiScan – Make it look like a PDF has been hand signed and scanned

#160

Post by AnthonyMouse »

fastball wrote: post #91
AnthonyMouse wrote: post #82

Earlier quoted context omitted.

> national ID smart card National ID systems are an incredibly bad idea. You can already get the entire authentication benefit from using decentralized ID systems (your bank authenticates you with your bank card, your employer authenticates you with your employee ID), so all a national ID adds is the ability for corporations to correlate all your different identities without your knowledge or consent, which is nothin…

I think you're forgetting the part where those existing so-called "decentralized" ID systems are by-and-large using a centralized system (your SSN) which is magntitudes worse than a cryptographic card. Your bank knows that you are the same John Smith as your employer has on record, because you needed to use the same SSN for both. The status quo is that any service which requires identity validation is requiring you t…

> I think you're forgetting the part where those existing so-called "decentralized" ID systems are by-and-large using a centralized system (your SSN) which is magntitudes worse than a cryptographic card.

It's orders of magnitude worse at authentication because that's not what it's for and everyone should immediately stop trying to use it for that. For that matter it would be better if they would stop using it for anything other than its original purpose as a tax ID.

> Now compare that to public-key encryption. Not only is it better assuming you only have access to a single private key (because you are still authenticating with the output of the key, not the key itself as with SSN), but also because a cryptographic card could store MULTIPLE private keys, allowing you to authenticate with a different "identity" to different providers, making it impossible for them to cross-reference you in that way.

But that's exactly the point. That isn't a national ID, it's ordinary public key cryptography which anyone can use right now already. You don't need a national ID for this, just create a new public-private key pair whenever you first interact with a new entity and use it to authenticate yourself to that entity going forward.

> Your bank knows that you are the same John Smith as your employer has on record, because you needed to use the same SSN for both.

But there is no good reason they need to know this, because having a bank account has really nothing to do with having an employer. All your employer should need is your bank account number so they can deposit your paycheck -- or not even that, just to give you a signature authorizing their bank to transfer money to you, where "you" means the person who can prove they hold the private key corresponding to a public key you gave your employer.

Banks shouldn't even need to know your name if things were being done securely, much less your SSN. Having them is nothing but a liability because someone who doesn't know what they're doing could mistake them for an authentication method.

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