I once thought the hard copy or electronic CAD file in my records was the original drawing. If emailed to a client, it turns out this notion would not hold up in the court of law. Drawings that are emailed are sent to the cloud, a cluster of computers, and move from computer to computer before they reach the end user. At any point along the trip, the drawing can be changed, and the point of this example is verifiable, repeatable evidence the drawing has not changed. The end user expects they hold an exact copy of the original CAD file. How do you know they have the same file as the one you sent as the email attachment? Well, it turns out you have a few methods to solve this dilemma. A sign your drawing with a Digital Certificate, or Password Protect with Hash comparison will be discussed here.

I sign my drawings with a Digital Certificate, which has a digital fingerprint unique to me and my personal email address. If the drawing changed and emailed back to me, I will be able to verify the drawing has changed. This process is done for me and is built into AutoCAD. The other method (Password Protect) requires more than a Password to verify your drawing. Since passwords may be compromised, there needs to be a secondary method to verify the state of the drawing.  Before sending the drawing to your client, use a Hash Algorithm software like in AEC Signature will record the hash code of the drawing in a separate text file. Remember, when using  any Hash Algorithm software, the CAD drawing must be closed, or at a minimum, the software must copy the drawing to a temporary directory(to allow full read) to return an accurate hash value.

In summary, you can use a Digital Certificate to verify the round trip state of your drawing. This is common practice with other file types. The second method would be use a password to protect the document along with the hash code of the document stored in a safe place before you send the files to your client.

AEC Signature 2012- Overview Electronically seal, embed and encrypt professional licensure information inside an AutoCAD database. The RealDWG toolkit enables you to share design data with confidence using the native DWG format. So you can create applications with 100 percent DWG read/write capability. Deliver your products with the latest DWG technology available from Autodesk. The program outputs a private key file for personal use, and a public key file for distribution to the client. Use the output files to compare for changes in the drawing. This is a stand-alone application, which does not require an Autodesk product to be installed to read and write drawing files. An excellent tool for distributing AutoCAD files electronically while embedding security information of the author or professional.