Most if not all encryption systems rely on a password or key that is stored within ram when you “unlock” the file or drive. This lets you access whatever you need while the decrypting program runs and encrypt it when you are done. Apparently…this isn’t as secure as thought.
The decrypting key is put in ram where it can be accessed quickly in the case you need to open an encrypted file. Ram…normally requires electricity to store information, so logically, when you turn off the computer, the keys that were stored there should be auto erased. However…they have found that chilling ram chips to -196 degrees C will allow ram to retain information for hours without power.
Well…in that case, someone goes and sprays compressed air (upside down…) onto your ram chips and they can analyze the bits on your chip for the unencrypted keys that are stored in ram. Of course, there are some holes in this…what is the time frame between computer shutdown and data loss? If its even close to instantaneous, there’s little to no trouble as you would still be at the computer. Also, would you need to keep the chip cold the entire time until its offloaded? Important quests. However, this is still an interesting little bit of information…
Check out the entire article at the NY Times