Contrary to conventional wisdom, "volatile" semiconductor memory does not entirely lose its contents when power is removed. Both static (SRAM) and dynamic (DRAM) memory retains some information on the data stored in it while power was still applied and they still hold values for a long intervals without power or refresh. This is a known [2] problem for a long long time. However, no one has ever tried (or published) any practical attack on this problem like what Princeton University researchers did.

This DRAM threat goes beyond disk encryption. Any kind of sensitive data such as password, encryption key, credit card information,... in you RAM could be stolen in just a few minutes. Due to the nature of this problem, it's hard for software based hard disk encryption solution to protect against this attack. Software based solution would be able to try to encrypt/clear the disk key whenever PC goes into inactive state (i.e screen saver, standby, hibernate) but it's not really practical and/or applicable in some cases. The white paper [1] also offers interesting algorithms & methods to find crypto keys in memory images.

If you're really care about your information, you should better to change your behavior to unmount encrypted disk and/or power-off your machine (for a while to give the memory enough time to decay) whenever you're away from your computer if you're using software based disk encryption and/or to use a hardware based disk encryption solution. It turns out that the hardware based disk encryption technology that I'm working on would be a perfect solution to help to protect against this kind of attack. For a full protection, our solution still need to fix a small problem when the computer goes into S3 (standby mode) but just a minor change. FYI, Seagate also has a hardware based hard disk encryption solution ready to use.

Links:

1. Lest We Remember: Cold Boot Attacks on Encryption Keys
   
2. Secure Deletion of Data from Magnetic and Solid-State Memory

Hulton & Steve have presented the new fast & cheap method of cracking A5/1 GSM encryption this week at BlackHat DC Security Conference 2008. This is the result of Cracking A5 and GSM scanner project which has been presented at VNSECON 07 by Steve last year.

FYI, GSM monitoring system has always been there for a long time. However, those devices are very expensive (few hundred thousands to millions USD depends on capabilities, number of channels, antenna,...) and only available to government agents.

Links:

• http://blog.washingtonpost.com/securityfix/2008/02/research_may_spell_end_of_mobi.html
• http://www.blackhat.com/html/bh-dc-08/bh-dc-08-speakers.html#Hulton
• http://wiki.thc.org/gsm
• http://wiki.thc.org/cracking_a5
  
• http://conf.vnsecurity.net/program