heat treating a chain to resist freon attacks

[STIHL]

well over in the motorcycle world I hear alot about theives smashing locks by using freon.They spray the freon on the locks and smach them with a hammer and they break.Now my question comes in few parts to help me get a better picture on this.
1 what does case hardened meen?
2 can I achieve anything different then case hardened by heat treating a chain to say around 65rc?
3 will it be the brittle at the hardness?
4 what hardness would you recomend for protection against this?

Unlike competitive locks, the ABUS motorcycle lock family takes a balanced approach to protecting your motorcycle. The ABUS locks' rugged, core-hardened chains and shackles, superior body materials and carefully designed shakle openings protect against prying, pulling and cutting. And the Plus Keyway System protects against picking, drilling, cylinder pulling and Freon while minimizing the likelihood of someone having a duplicate of your key.) Freezing a lock with a cold spray such as Freon then smashing the shackle is becoming a popular method of thieves today. All ABUS motorcycle locks are tested down to -40 F degrees. Freon is only -20F degrees.

These guys are getting large coin for these locks and im not about to fork it out.While I understand their locks are superior and would consider buying one but the chains are just a bit to much for me.

 

[Ripper]

Jay,
The idea behind case hardened is to diffuse carbon (and/or nitrogen)
onto steel to make a very hard outer shell with a soft core.
This gives you a very hard working surface (in the case of chain; hard to cut) with a core that will not shatter.
Regards, Greg