BEST LFIC Impression masters...

[Oldfast]

Never having attempted a BEST, what you have to say about it Gordon, I find interesting.
Alot of good experience & insights there man. So in short, Xeo was correct when he
anticipated they could be problematic when impressioning.

[rai]

seems to me that you could try techniques from methods such as described in matt blaze paper on "amplifying rights in master key systems" if I remember the name of that correctly,
just a working key to start then working with each pinstack to find other shear lines created by master pins or the extra shear line of the control sleeve.
its a lot of work, but if you have the blanks and a best key clipper, or something like that, you could explore the system one pins stack at a time.

[rai]

uh nevermind, I see the flaw in that idea, you could only find other shears in the pin column for the shearline that answers the key that you work off of.
still there might be information found there that could with more work be tried at the control sleeve shearline gotta think on this some more.

[TeamStarlet]

Has anyone had any discoveries or revelations on this? I've been playing around with a few cores and I've become fascinated with trying to impression a control key. I've successfully managed to impression some change keys for the cores, and one even turned out to work in several of the cores, so it's a master key to some degree, but haven't yet cracked the control key.

I'm not sure on this, but is the control key likely to be the highest pin on each stack? According to Matt Blaze "the bitting of a control key at any given position might be higher, lower, or the same as an operating key; the only requirement is that the complete control key bitting cannot also be used as an operating key."

[GWiens2001]

Have successfully Impressioned keys for BEST locks before, but failed miserably most times. Yes, it is possible to impression them. The problem is when operating shear impressions first. Is there only one pin stack that differs from operating (yes, have seen just one pin difference)? Two pins? Five? Seven? You just don't know.

I would suggest copying your change key (several of them), but leave one bitting uncut. Then keep impressioning only that pin stack until you get all the way to the 9 cut. Note any bittings that either open the lock, or leave no impressioning marks. Repeat with each bitting location. This is identical to the process for a privilege escalation attack. Do not, under any circumstances, file any other locations on the key, even if they start to mark. Just make a note as to which pins started to mark, and at what depth the bitting you are filing was at when the other pin starts marking.

Perhaps the pin stack that started marking will be the next one you try. You may even decide to cut a key to the same as the operating key, except for your previous pinstack, which you will have cut to the depth that left no mark but caused the current pin stack to leave marks. Then have your current pin stack uncut, and impression it down to a 9, like above.

Sorry if this is confusing. On a short break at work, and have to get back.

Essentially, if your operating key is:
6382168
Make your next key as:
6382160
And keep impressioning until you get to:
6382169
If, when you were at:
6382164, pin stack 7 left no mark, but pinstack 3 did, then try:
6302164, and work down to:
6392164.

As you can see, this can eat a lot of key blanks in a hurry, especially if you have all seven pinstacks different between change and control.

That is also why I have, for the most part, given up on impressioning keys for SFIC.

Good luck,

Gordon