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In article <3m9udl$9hs@agate.berkeley.edu>
amoeba@uclink2.berkeley.edu (Anderes Nudelbrett) writes:

> There is a simple and quick method to break just about any steel lock. 
> It is quite common in Germany where new U-locks have been designed by 
> ABUS to prevent this method from working. the method (which I won't 
> describe in detail) involves taking advantage of steel's ductile to 
> brittle transition with respect to ambient thermal energy. QUESTION: Are 
> kryptonite locks protected from this method? And, why is this method 
> never mentioned on the backs of the lock packaging (unlike the jack and 
> the pipe methods that everyone knows about) if the locks ARE resistant to 
> this kind of attack.

This method is hardly a secret. Almost every time I mention bike theft
to someone, they tell me about breaking locks with freon or liquid 
nitrogen. Yes, kryptonite locks (stainless shackles) aree susceptible, 
too.
 
> Since this method is really easy (and accessible to people near 
> laboratories and universities) and since it works on padlocks too, I advise 
> the people who use only chains with a padlock to consider using a U-lock 
> as well. 

This method is not really easy. It's very difficult to cool down a lock
with liquid nitrogen, because it just pours off. You need to make some
sort of liquid-tight styrofoam container around the lock. If you can chill
lock enough, you still have to bang on it really hard to break it. It 
doesn't just shatter. 

I think the reason people think this method is prevalent is that when 
someone tells of their "unbreakable" lock being broken, and their bike
being stolen, and it is explained to them as being the work of a thief
using mysterious liquid nitrogen (instead of a car jack or crowbar, which
probably was used) they buy this explanation, and tell more people
about it.

Bottom line: thieves carring LN2 are as much a worry as thieves with
oxy-acetylene cutting torches. And since you couldn't defend against 
them anyway, who cares?

Michael Fuhrer