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Important Note

This page answers questions about the discontinued CADLock SE product.


 What Is CADLock?

Q: What is this CADLock thing anyway? Why should I use CADLock? What can I do with it?

A: CADLock is an add-on program for AutoCAD that allows you to save your drawings in a secure format.

There are many uses for CADLock, and you will certainly find the best applications for Locked drawings in your specific tasks. Here are some scenarios where you may find CADLock a valuable addition to plain AutoCAD:

1. When one firm is required to submit electronic files as part of the bid to win a contract, they may secure the files so that the recipient may not use their work without awarding them the contract.

2. If an untrustworthy client requests drawing files before paying for the work, restricted use may be granted until payment has been received.

3. Give someone (possibly a competitor) an opportunity to review progress of a design, yet prevent them from modifying or copying the electronic file.

4. Give a client the ability to archive the electronic file and to create plots without also giving them access to proprietary design data.

Alternative Security Methods

Q: Other than using CADLock, what else could I do to secure my drawings?

A: We are not aware of any directly competing products at this time. Alternative strategies for securing drawings usually rely on producing and distributing a reduced-intelligence version of the drawing file. Dietmar Rudolph has written a White Paper on this subject.

Q: Doesn't AutoCAD 2004 already include password protection?

A: In AutoCAD 2004 users are able to encrypt drawings. Once a drawing is encrypted, the password is required in order to open it again. If an encrypted drawing is sent to a third party, the password must be sent along with the drawing file. Once an encrypted drawing is opened, it becomes a normal drawing again, with no restrictions on usage.

A locked drawing created by CADLock SE retains its programmed access restrictions no matter what happens to it. Such a locked file is designed to be distributed beyond the originator's organization to untrusted third parties. With CADLock, security is programmed into the file format, and it follows the file no matter where it goes.

Q: What about digital signatures in AutoCAD 2004?

A: In AutoCAD 2004 you can digitally sign your drawing. This usually involves purchasing a digital key, paying a company to keep this key, and running a private or Web-based key server. AutoCAD 2004 will check any signed drawing during load and in case of modifications delete the signature. CADLock not only monitors drawing modifications, it disallows them. Therefore a CADLocked drawing is by definition signed from the moment it is created.

If it's necessary to verify that a drawing originates from a specific source (i.e. to ensure it didn't come from an imposter), this is easily done with CADLock and without the need for any other services by utilizing the public key protocol as described in the CADLock documentation.

AutoCAD LT, AutoCAD 2005, Release 12 and Release 13 Support

Q: Can a user with AutoCAD LT open Locked drawings I send to him?

A: Yes! AutoCAD LT is now supported as of CADLock 3.3.

Q: When will AutoCAD 2006 be supported?

A: It is supported now by CADLock 3.36.

Q: Will AutoCAD Release 12 ever be supported?

A: Sorry, no. Making an adequately secure version would be a major undertaking, and the number of requests we receive for it indicates that the market is not large enough to justify such an undertaking.

Q: Is Release 13 still supported?

A: Yes, for the time being AutoCAD Release 13 is partially supported. Click here for details.

Batch Processing

Q: How can I batch process a set of normal drawings to produce a Locked set of drawings for distribution outside my company?

A: Jon Fleming has written a White Paper on this subject.

Becoming A Dealer

Q: I am interested in becoming a dealer or distributor. What do I do?

A: Email us with information about your company and proposed marketing strategy.

CADLock On My Web Site

Q: I want to make CADLock RT available from my Web site. Can I do so?

A: Yes. Please use a link pointing to If you have any other questions, just email us.

DWX File Format

Q: I can't open a .dwx file, AutoCAD says it's invalid.

A: If the locked file requires a passkey, then you must provide the correct passkey or AutoCAD will complain about an invalid file. If the passkey is being specified correctly, the problem is most likely due to incompatible file versions. Just as with .dwg files, your version of AutoCAD may not be able to open .dwx files created by a later version of AutoCAD.

One more possibility exists. The .dwx format changed with CADLock 3.34; this means any .dwx files created with CADLock 3.34 (or later) will not open in earlier versions of CADLock. If this is the case, simply download and install the current version of CADLock RT and try again.

Q: I have locked files created with a prerelease CADLock version. Can I use them with the shipping version?

A: No, you cannot. A prerelease beta version is beta because it may still contain bugs or security holes. The shipping version uses a different encryption algorithm, therefore no beta version will open locked drawings created by a released CADLock, and vice versa. This ensures that any security holes in beta versions cannot be used to break the security of the released version.

Export Restrictions

Q: I understand there are US export restrictions on some software products. I want to know if CADLock is available in my country.

A: Due to US Department of Commerce regulations, CADLock is not available in, and may not be imported into Cuba, North Korea, India, Iran, Iraq, Pakistan, Sudan and Syria. We regret that export restrictions affect our ability to ship products to these countries, but we must be extremely careful to abide by the relevant regulations as the penalties for failing to do so are very severe. Note the addition of India and Pakistan to the above list, following the recent nuclear tests by those countries .

Q: Since CADLock uses encryption, is it restricted from export by the International Traffic In Arms (ITAR) regulations?

A: Not at this time. CADLock, Inc. has been granted an export license by the US government because the encryption algorithm meets the requirements for a mass-market software exemption.

Press Resources

Q: I'm a member of the press. How do I obtain the resources I need to perform a review?

A: Email us and ask!


Q: How much does CADLock SE cost?

A: CADLock SE has been discontinued and is no longer for sale. Please take a look at CADVault for AutoCAD, the next generation technology that has replaced CADLock SE.

Q: How much does CADLock RT cost?

A: Nothing!

Security Of DWX Files

Q: If somebody buys CADLock SE, does this mean they can open all Locked (DWX) drawing files?

A: No! Not without the passkey! CADLock SE is no more capable of opening and editing DWX files than CADLock RT: the two products have identical capabilities when it comes to reading DWX files. The difference between the two is restricted to the creation of Locked files. CADLock RT cannot create truly secure drawings, because anyone with CADLock RT or SE can open them using the special password "DEMO". CADLock SE can create truly secure drawings which cannot be opened except by people with the appropriate passkey.

Q: If the recipient knows the passkey, can they get full access to a secured drawing?.

A: No! The programmed restrictions are entirely independent of the passkey needed to open the file. Someone who does not have the passkey won't even be able to open the file. The passkey only allows the file to be opened at all. In no case can it be opened with anything other than the programmed restrictions in place.

Q: I have forgotten or lost my passkey. Can you find the key or get into the drawing for me?

A: No! Because of the nature of the encryption algorithms, there is no way for CADLock, Inc. to retrieve a lost or forgotten key. This is for your own security. If we could get into a drawing without a passkey, then somebody else could, too. It is vitally important that you keep a safe copy of the drawing in unprotected *.dwg format and/or keep your passkeys very safe.

Q: What encryption algorithm is used by CADLock?

A: The CADLock encryption engine uses a 32-bit Blowfish algorithm. The public key engine is Diffie-Hellman hashed to 32-bit and passed to the Blowfish encryption routine. For more information about encryption algorithms, click here.


Q: I need help with a CADLock product. What do I do?

A: First, read the documentation. If you're still having problems, contact the dealer or distributor who sold you the product. If you ordered the product direct from CADLock, Inc. or your dealer or distributor is unable to help, email us with details of your problem, the name and version of the CADLock product, the exact release of AutoCAD (eg. R13c4a), your Windows version and as many other details as possible to help us understand and reproduce the problem.


Q: I installed CADLock but get the message "ARX failed to load" or "This version is not supported" when I try to load or use it.

A: This can occur if you use incompatible versions of AutoCAD and CADLock. If you're using a recent Autodesk product, CADLock may not yet have support for it. If your version of CADLock is out of date, check the downloads page for updates.

Q: When opening an encrypted drawing file, AutoCAD displays an error that the file is not an AutoCAD drawing file, or the file is said to be damaged or corrupt. What's wrong?

A: Make sure the correct key was used in opening the drawing. Secret Passwords are case sensitive and must be entered exactly as they were entered when the file was encrypted. With the public key protocols, make sure that the correct public and private key files were used.

Q: I have CADLock installed and it successfully opens the sample files. Somebody gave me a Locked file (*.dwx), but when I try to open it, the OPEN dialog keeps popping up and the file does not load. Why not?

A: This will occur if you are using Release 13 and the other person gives you a Release 14 *.dwx file. Ask them to save it as a Release 13 *.dwx file.

Q: CADLock allows me to open an encrypted drawing file and make modifications, but won't let me save it. Why not?

A: It is possible (and in some cases desirable) to allow modifications of a drawing but to disallow database output. This is ultimately the decision of the owner of the drawing at the time the encrypted drawing file is created.

Q: I made some changes to a drawing and forgot to save to an unsecured drawing (*.dwg) prior to saving it as a Locked file (*.dwx). Now CADLock won't let me save my modifications to a *.dwg file. What do I do?

A: In this case do not exit the drawing, but immediately issue the CLRESET command and then save as .dwg.

Q: When installing CADLock (RT or SE) I get a message saying that an AutoCAD configuration file can't be modified. What do I do?

A: This is a known minor bug in the installation routine of CADLock 3.10 and 3.11, which occurs when the installation software tries to change an AutoCAD configuration file which for some reason has a null character (ASCII 0) character in it. It was fixed in version 3.12. If you're using an earlier version, don't panic! The installation routine is just trying to store the location of the CADLock directory, and if it can't do so (or if you choose not to allow it to do so) there is an alternative mechanism built into CADLock itself. The first time you try to use CADLock, you will be prompted to find one of CADLock's files. Navigate your way to the directory in which you installed CADLock and select the file. CADLock will then correctly modify AutoCAD's configuration file so you will not be asked the same question again.

Typical Scenarios For CADLock Use

Q: What are all the different restrictions for? Where would I use different combinations of restrictions?

A: Here are some typical applications and what may be a recommended combination of restrictions. Please note that your specific requirements may result in different settings which are better suited.

1. The most simple use of CADLock is to tag each of your drawings with the name of the designer in charge. Such a situation requires that you set the drawings to retain full ownership control and no restrictions set. Just enter the designer's name and maybe a passkey. However, if you have a document management system, such a system would be more appropriate for this task.

2. Another internal use of CADLock (again if you don't have a document management system) would be to lock drawings when released. CADLock can disallow all modifications to a secure drawing and therefore is best suited to fix the released state of a drawing. In this situation set (lock) database modify restriction, but enable full ownership control so the drawing can be saved to a different .dwg file again for later revisions.

3. If your company has offices at different locations and you need to transfer electronic drawings by mail or through the Internet, you may add a passkey to the drawing so unwanted listeners cannot read the file. Typically you would allow full ownership without applying any restrictions to such a drawing.

4. If you give the drawing to a different party who paid for the design and is allowed to modify it at will (no restrictions), you may simply copyright your drawing. In this case, enter your name on the originator page and disable full ownership control.

5. Releasing drawings for presentation or demonstration only is another typical use of CADLock. Remember to disable full ownership control and to restrict database modification, output, and query.

6. Many companies pass drawing files to consultants for FEA analysis, programming of NC tool paths or rapid prototyping. Depending on the software used by the consultant you may want to disable full ownership control and database modification.

7. A new use for drawings is to publish them on the World Wide Web. Of course you don't want to have the downloader gain full ownership control on the drawing. Typically you will also restrict database modification, query and output as well as plot/2D output.

Version Information

Q: What versions of AutoCAD does CADLock support?

A: Most variants of AutoCAD Release 14 through AutoCAD 2005 and AutoCAD LT 97 through AutoCAD LT 2005 are supported. Limited support also exists for AutoCAD Release 13 for Windows. For the most up-to date information on supported versions, click here.

Uninstalling CADLock Manually

Q: What do I need to do if I want to uninstall CADLock 3.2 or earlier myself so I know what's going on?

Q: I have deleted some CADLock files (e.g. SETUP.EXE) and now the uninstall won't work. What do I do?

A: Follow these steps:

;; CADLock Initialization <begin Osprey generated code>
(If (Not (Load "D:\\Cadlock\\Startup.lsp" nil)) (Princ "\nCADLock Error: D:\\Cadlock\\Startup.lsp failed to load!\n"))
;; <end Osprey generated code>

Using CADLock With Xrefs

Q: How can I use CADLock to protect drawings that use xrefs?

A: There are three approaches to creating locked files which contain xrefs.The following instructions describe the steps for each approach (the instructions are for a single 'parent' drawing with one or more attached 'child' drawings):

1. The simplest approach is to simply bind all xrefs before creating the locked file. This approach eliminates the need to deal with separate files altogether, but it may not be suitable for cases where xref "children" are attached to more than one parent drawing. To use this approach, do the following:

a. Open the parent drawing

b. Enter the command line version of the xref command (-XREF in R14 and later, XREF in R13).

c. Select the Bind option.

d. Enter an asterisk (*) to bind all attached xrefs

e. Use the SAVEAS command to save the resulting file as a locked .dwx file.

f. The saved .dwx file is now a standalone secured file with all xrefs bound into that one file. *Don't* overwrite your original .dwg file after the xrefs are bound!

2. If binding is not suitable, it is possible to reroute the attached xrefs to their .dwx counterparts using the following steps:

a. Create copies of all xref "children" (i.e. files that are attached to the parent drawing), and give the copies a .dwx extension (they will be temporary unsecured .dwg files in disguise).

b. Open the parent drawing in AutoCAD.

c. Use the XREF command to repath (change the filename of) the attached xrefs so that they refer to the temporary .dwx files created in step a.

d. Use the SAVEAS command to save the parent drawing as a locked .dwx file.

e. Open the xref "children" one at a time and SAVEAS them as locked .dwx files (overwriting the temporary .dwx files created in step a).

f. Once all xref children are secured, the secured .dwx parent created in step d) now correctly refers to the secured versions of the xref children.

3. The third approach is the easiest way, but it must be done with extreme caution to avoid overwriting unsecured .dwg files with secured files of the same name and extension!

a. Copy the parent and child drawing files to a separate folder.

b. Open the parent, then use the SAVEAS command to save it as a locked .dwx file.

c. Open each child drawing and save it as a locked .dwx file.

d. Delete the original unsecured child drawings (the .dwg versions).

e. Rename all locked child drawing files as .dwg. DON'T OVERWRITE YOUR ORIGINAL COPY OF THE .DWG FILES!

f. At this point your secured parent drawing xrefs the .dwg files, but the .dwg files are really locked files with the wrong extension! As long as CADLock is started, the renamed .dwg files behave exactly as .dwx files would (the programmed restrictions will be enforced no matter what the file extension is).

What To Do After CADLock Is Installed

Q: I've installed the software. What do I do to make protected drawing files?

A: The help files give detailed instructions, but here's a simple description of one way to do it.

  1. Start AutoCAD and open a DWG file in the normal way.
  2. Pick the start button to invoke the CLSTART command. (Depending on how you installed CADLock this step may not be required, but it won't hurt).
  3. Invoke the AutoCAD SAVEAS command (eg. using the File > SaveAs pull-down menu item).
  4. Change the file type to Locked Drawings (*.dwx) and pick the Save button.
  5. The Security Settings dialogue will appear. Pick the little padlocks to choose the restrictions you want to place on the drawing.
  6. Pick the Passkey tab, pick the Secret password protocol and type a password into the edit box. (This is optional: the universal passkey will be used if you omit this step).
  7. Pick the Originator tab and type your contact details into the edit boxes. (Again, this step is optional).
  8. Pick OK. You may get a warning message. If so, read it and pick OK.

That's it! It may sound complicated at first, but it can be summarized as follows: assuming CADLock is started, use SAVEAS, choose a *.dwx file type, and just follow your nose from there.

Alternatively, you could use the CADLock Wizard. Pick the wizard button and follow the instructions.

I Still Have A Question

Q: I still don't know the answer to my question. What do I do now?

A: If you still have a question, email us and we'll do our best to help.

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