Protecting drawings from unauthorized or accidental changes

Jim Canale

Ok, I have asked this in a support request, and am awaiting a reply.  But I was wondering if anyone outside of the BricsCAD support staff has suggestions for me?   Perhaps you are aware of a third party application that fills the bill?

When I want a quote for the manufacture of a part I designed, I send a PDF of the drawing.  I figure this offers some small measure of protection from unauthorized, or accidental alteration.    (A jobshop once altered a tolerance in a complex drawing to make the part easier to build.)    And to a certain extent it protects the investment we made in man hours to create the 3D model.  

Increasingly, the jobshops are demanding DWG's, STEP or IGES files.   I suspect they want to use these files as input to their CAM programs.    So how to give them a 3D model which can't be altered?

Knut Hohenberg

Sounds impossible to me.
Of course, you can encrypt data to protect against unauthorized access, but keeping software from altering accessible data can IMO not be achieved by technical means. So to protect your intellectual property when you have to hand out CAD source files, you'll need lawyers...
But to protect against altered files being passed on, you might consider creating a checksum (e.g. type openssl dgst -md5 filename in a terminal) that you include in all communication.

Jim Canale

I'm not talking about anything super hi-tech.  And I'm not talking about making them "hacker proof" or NSA resistant.   We're talking  about preventing mostly accidental modification by job shops.   I'm talking about the kind of protection that exists in Word documents, where you can make them Read Only, and editable only by entering a password.    I'm no programmer, but I don't see why it would be possible for a word processing application and not a CAD program.

Bruce Fillmore

Sounds like you need some additional language in your RFQ stating something to the effect that parts are to meet the specifications you provided including all plans, any modifications shall be approved by you in writing in advance.  If they choose to try something underhanded then find a new supplier. 

For many reasons they will not want a read only type of plan.

Roy Klein Gebbinck

Here is an article by Owen Wengerd on this topic:
http://otb.manusoft.com/2008/12/design-file-locking-and-snake-oil.htm
Note that an unequally scaled minsert entity can be exploded in BricsCAD.

Robt Deans

If pdf, dwf files are not acceptable, I suspect you're limited to 3rd party soft.s, i.e.:
http://www.cadlock.com/

Knut Hohenberg

@Jim, Rob:
The kind of security you are talking of relies on the software that is used to open the file, and is as such not a possible solution for non-proprietary file formats (step , iges, and to some extent dwg) that can be opened by a variety of applications.
 
@Jim:
As said before, you can use encryption to limit access to your data, but to my knowledge, you cannot control what people who have access will do with it.
If some workshops make mistakes in processing the data - well, this will always be possible, but shouldn't be your problem as long as you can prove it wasn't your fault (= signature).

Not wanting to hand out valuable data to possible competitors is another story, this is quite common also in my field of work (architecture).
E.g. often initial design of a building is carried out by one office, that then has to hand over documentation to another one that does the design development. It is understandable that transferring CAD data (which the client usually demands) is often done reluctantly in such a case, and that people will look for ways to limit the value of the data. This can of course be achieved in a variety of ways (destroying structure by exploding everything to tiny pieces or joining into a big lump, exporting with limited accuracy etc.), but I personally never used such tactics.

Richard Webb

Well, there's CAD-Protect listed in the Bricsys store. I haven't used it myself but from the description it does sound like it would do what you're looking for.

Knut Hohenberg

They (CAD-Protect) claim that no plug-in is needed on the recipient's side, so I guess they fall into the snake-oil category that Roy posted the link to... but they offer a trial, so everybody should see for themselves.

Jim Canale

@Bruce Fillmore:

Sounds like you need some additional language in your RFQ stating something to the effect that parts are to meet the specifications you provided including all plans, any modifications shall be approved by you in writing in advance.  If they choose to try something underhanded then find a new supplier. .....

Although I regularly remind vendors about critical tolerances in my emailed RFQ's, why should I have to say anything?  The requirements are on the drawings.  And what does asking that modifications be approved in writing do for us.  They still could open a drawing and accidentally, or intentionally change a tolerance to make it easier to build the part.   I don't object to the concept of giving them a CAD drawing to use as input for their CAM program.  What I object to is giving them R/W access.  I used to use Autocad R14. I believe it had the capability to restrict access to Read Only.

Jim Canale

@Richard Webb:

Well, there's CAD-Protect listed in the Bricsys store. I haven't used it myself but from the description it does sound like it would do what you're looking for.

I will see if we can test Cad Protect.  (Depends on what kind of mood our IT manager is in.)  We haven't had good luck with 3rd party plugins for BricsCAD.   Automesher in particularly.  The product never worked for us.  And support was non-existent.  I am STILL waiting for them to respond to 5 requests for support dating back to last October. 

I'd much prefer that BricsCAD come out with the built in capability to protect files from unauthorized alterations. 

Do the rest of you pass your unprotected DWG's to vendors? 

Richard Webb

Usually PDFs, since Acrobat and all of the other PDF readers are on virtually every machine nowadays.

There are a couple of metal shops which we use that do ask for the original drawings and we happily supply those. NDAs are in place where required. As I understand it, those vendors extract what they need from our drawings to create their own in-house manufacturing package. No problem with that. The parts either meet our original specs or they don't and if they don't then the vendor either fixes it or doesn't get paid.

Jim Canale

@Richard Webb:

Usually PDFs, since Acrobat and all of the other PDF readers are on virtually every machine nowadays.

There are a couple of metal shops which we use that do ask for the original drawings and we happily supply those. NDAs are in place where required. As I understand it, those vendors extract what they need from our drawings to create their own in-house manufacturing package. No problem with that. The parts either meet our original specs or they don't and if they don't then the vendor either fixes it or doesn't get paid.

You can't withhold payment unless you can prove they built the parts incorrectly.  And they can readily edit your drawing to fit the parts unless it is READ ONLY.   In the day of inked prints it was a lot easier to see if someone had altered a drawing. 

Anyway, until I find a way to make the DWG's Read Only,  I will send only PDF's to vendors.  If they insist on the DWG, they will not get the job.  If the issue hadn't bitten us once already, I might not be so concerned...

Robt Deans

Or send them the .dwg file ALONG with hard copy with a wet stamp to which all job spec.s / references ascribe to.