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Jim Frame
(@jim-frame)
5,000+ posts Registered
Joined:8 years  ago
Posts: 5407
January 11, 2018 9:47 pm  

I've been using a self-certified digital signature on PDFs for a few years now, but I've never gotten around to seeing what happens when someone modifies (or tries to modify) the document.  I've attached a test file, and would be interested in learning if others can modify it, and if so what happens when they try to print it.

 Thanks!

Jim Frame
Frame Surveying & Mapping
609 A Street
Davis, CA 95616


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Wendell
(@wendell)
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Joined:9 months  ago
Posts: 3963
January 11, 2018 9:58 pm  

Here's a screenshot after I opened the file:

Image 2018 01 11 at 9.53.16 PM

I was then able to edit the file, which I saved and attached here.

Edited: 1 week  ago

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Dallas Morlan
(@dallas-morlan)
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Posts: 687
January 11, 2018 10:22 pm  

Click on the "Digital Signature" block in each file and the difference becomes apparent.  Jim's original fill will show this validation box

Validation

while Wendell's file will not.  The original file also shows a rectangular line around the signature when the cursor is moved over that area.  Wendell's copy does not react as that area is a graphic and not an active digital signature.

Clicking on the "Signature Properties" button of the validation box will show the following.

SigProperties

Dallas P. Morlan, P.S. (Retired), OH, WV


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Jim Frame
(@jim-frame)
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Posts: 5407
January 11, 2018 10:42 pm  

I was then able to edit the file, which I saved and attached here.

Which means that anyone can edit it, and when printed it looks like I've signed the modified file.  I was kind of hoping that it would be watermarked or rendered in some distinctive way that would make clear that the edits occurred after the signature.  Being able to validate the signature only in a digital environment is hardly optimal.

How do others handle this kind of thing?

 

Jim Frame
Frame Surveying & Mapping
609 A Street
Davis, CA 95616


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Gromaticus
(@gromaticus)
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Joined:7 years  ago
Posts: 310
January 12, 2018 3:38 am  

I use the digital signature in Acrobat with my seal and signature as an "appearance." I had always assumed that if the file was changed, the "appearance" would disappear, but no, my seal and signature remains and will still be printed. Like your example, the only way to tell that the file was changed was to load the file in Acrobat.

So I add the phrase "Issued as electronic media with encrypted digital signature" that I hope will tip someone off that there is a digitally signed file out there somewhere they can check if there is any doubt about the paper copy.

But other surveyors in my area just seem to scan their seal & signature and add it to the PDF without a digital signature. 

In the last 8 years or so that I have been using digital signatures, I have only run across one other person who even knew what a digital signature was (an attorney who digitally signed my digitally signed proposal).

I have had my plans altered (redrawn!) twice by architects (of course), and all they had to work with was a paper copy, so there really is no sure way to protect your plans.


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John Putnam
(@john-putnam)
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Posts: 965
January 12, 2018 5:55 am  

Oregon Statute requires that you add the statement 'Digital Signature' along with your stamp.

John Putnam, PLS
OR, CA, WA & ID


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FL/GA PLS.
(@flga-pls)
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Posts: 2763
January 12, 2018 6:20 am  

Jim, Why not just use this. It’s fully accepted in all business transactions, corporate transactions, etc.

 “ACES Business Representative Certificate - 2 year certificate”

https://www.identrust.com/certificates/buy_aces.html

"I,d rather die while I'm living than live while I'm dead"....Jimmy Buffett
"All I know is, if you look around at the human race you've got to wonder what the hell God was thinking!" ...Lee Marvin, "Paint Your Wagon"


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Jim Frame
(@jim-frame)
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Joined:8 years  ago
Posts: 5407
January 12, 2018 7:27 am  

Jim, Why not just use this.

What I don't understand is the practical difference between using a certificate like that and one generated by me.  Is a recipient really going to reject one of my documents because the certification authority isn't a third party?  Since I'm responsible for the document contents by virtue of my signature and seal, the assumption is that if they can verify the signature certificate they can rely on the document.  And if they need to verify the signature certificate, they can call me and I'll be happy to say, "Yeah, I signed that."

 

Jim Frame
Frame Surveying & Mapping
609 A Street
Davis, CA 95616


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Jim Frame
(@jim-frame)
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Joined:8 years  ago
Posts: 5407
January 12, 2018 7:35 am  

I just now realized that when I posted the original test file I hadn't locked it when signed.  I'm posting another that I locked.  Anyone care to repeat the test?

 

Thanks!

Jim Frame
Frame Surveying & Mapping
609 A Street
Davis, CA 95616


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David C. Newell RPLS LS CFM
(@david-c-newell-rpls-ls-cfm)
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Joined:6 years  ago
Posts: 114
January 12, 2018 7:59 am  

The edit functions were greyed out in both Adobe and PDF exchange.


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Jim Frame
(@jim-frame)
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Joined:8 years  ago
Posts: 5407
January 12, 2018 8:06 am  

The edit functions were greyed out in both Adobe and PDF exchange.

That's encouraging!

Jim Frame
Frame Surveying & Mapping
609 A Street
Davis, CA 95616


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David C. Newell RPLS LS CFM
(@david-c-newell-rpls-ls-cfm)
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Posts: 114
January 12, 2018 8:11 am  

I tried to attach screen shots but I can't get it to work?


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FL/GA PLS.
(@flga-pls)
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Posts: 2763
January 12, 2018 8:13 am  

“Is a recipient really going to reject one of my documents because the certification authority isn't a third party?”

I suppose not, however in Fl. all, or mostly all submission of Survey documents to various municipalities for construction (plans, site plans, building permits…..etc.) require a registered digital certificate. $70 bucks a year is less than I spend on beer for one week.  😎 

Sometimes being too frugal can create a backlash.

Edited: 1 week  ago

"I,d rather die while I'm living than live while I'm dead"....Jimmy Buffett
"All I know is, if you look around at the human race you've got to wonder what the hell God was thinking!" ...Lee Marvin, "Paint Your Wagon"


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Peter Ehlert
(@peter-ehlert)
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Posts: 2542
January 12, 2018 8:37 am  

not too skilled with image manipulation, but old school works

The Manual Of Instructions ... a History Book


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WA-ID Surveyor
(@wa-id-surveyor)
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Joined:6 years  ago
Posts: 454
January 12, 2018 8:52 am  

“Is a recipient really going to reject one of my documents because the certification authority isn't a third party?”

Most probably won't but you will want to make sure it passes the muster of your applicable state.  I know in ID this would be against state code if you are signing the document as a PLS.  I believe the same goes for WA as well.


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