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MINELAB E-Trac Files Primer

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4-20-2010

The MINELAB E-Trac includes PC connectivity features allowing the creation and sharing of files containing E-Trac patterns and settings. These files come in three flavors; pattern files (.ptrn), mode files (.mode) and universal, or global, files (.glb). If you download information from your E-Trac to your PC using E-Trac Xchange you can save it as one of these file types and send it to a friend. If a friend sends you some files you can, using E-Trac Xchange, upload them to your E-Trac.

This sounds good, but there is something missing that some thought should be there. The promise of PC connectivity started thoughts of patterns whizzing through our heads and thinking about how the E-Trac Xchange application would let us program the E-Trac from the comfort of our PC, but that was not to be.

To understand why we have to look at how the E-Trac Xchange files and the E-Trac work together. I wont go into detail on the construction of these files except to say that they are small and binary.

.ptrn file ~ 274 bytes contains E-Trac pattern
.mode file ~ 302 bytes contains E-Trac pattern and main settings
.glb file ~ 26 bytes contains a subset of settings rarely changed

These files go through the E-Trac's software, or operating system as it were, as managed by the logic in place. They have to be able to deliver their content and must, therefore, have access to elements of the E-Trac's operating system. This is not something to be taken lightly. MINELAB has, arguably, the most sophisticated detector software and algorithms on the planet. If someone could construct an E-Trac file that the operating system accepted as legitimate, but that had a malicious payload, it could ultimately lead to full access exposing the software contents of the E-Trac. To prevent this from occurring, MINELAB has programmed the E-Trac to only accept files created on an E-Trac. If you've seen the 'corrupted file' error when, for instance, trying to upload an Emulator file into an E-Trac, then you know what I mean (I've always thought that the error message should be more specific, like 'File not created on E-Trac'...probably could save some support calls).

This led to disappointment as no PC program could generate files that the E-Trac would accept. E-Trac Exchange is severely limited because of this and really only serves as a middleman between the files and the E-Tracs. Not many E-Trac users traded patterns. Connecting the E-Trac to your PC and transferring files didn't seem to have enough fun factor to make it worth it. Sharing was not enough. Punching in a pattern is pretty easy and fast on the E-Trac (after a bit of practice). Most disregarded the Xchange features of the E-Trac completely. The Xchange UI lacked in scope. It could have been a lot more, even with the restrictions (like an editor that would allow us to at least play with patterns, a more fully featured viewer for the data on the E-Trac as well as on disk with good graphics, etc.). MINELAB knew, though, that any extra frills would probably make them explain the security concerns and possibly confuse their users.

To ensure that an E-Trac acceptable file could not be faked, MINELAB embedded an equation into each E-Trac that writes information to each file as it is created. What parameters this equation utilizes is anyone's guess; it probably uses the payload data, or parts of it, as input and then sets the values of certain bytes based on the output. The point is that if you dont know the equation there is pretty much no way to figure it out. If you're another E-Trac, however, you know the equation too and can read the file. The MINELAB Emulators written by Max Derouen, for instance, can upload and download pattern files, but cannot create machine-acceptable versions of them.

Wanting to understand all this, some time was taken to see how and where the data was stored and how to reliably extract it (for the three file types). With better understanding an alternative, or compromise, was considered. Most of us punch in our settings and patterns manually. Xchange does not give us features beyond the scope of the security limitations and is rarely used. If an application existed that could read all the E-Trac files, share patterns with the E-Trac Emulator, had the wished-for design and layout features and its own file exchange format, then we might have some of what we want. Although the creation of E-Trac acceptable files is not feasible, we can maximize the alternatives. The E-Trac Settings and Patterns 2.0 workbook is on the DOWNLOADS page and is the result of this train of thought.

Regards, TBGO

* Some of this Ive heard from other developers, some Ive seen firsthand and some is pure educated guess, but, regardless, the situation remains the same.

** New information: The file check may be in the Xchange program and not the detector. Investigating.



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