Russian password-cracking wizards ElcomSoft have announced a new product that can retrieve decryption keys for BitLocker, PGP and open source favourite TrueCrypt as long as the encrypted volumes were not securely demounted.

As chinks in the armour of such encryption systems go the one exploited by Forensic Disk Decryptor is small but potentially useful to forensic engineers in some circumstances.

Normally, a volume (or smaller container) encrypted by one of these software programs is secured using a password, which can’t be broken using any known brute-forcing attack as long as it is long and complex enough.

However, according to Elcomsoft when this password has been entered and the volume ‘opened’ the keys to access the volume and its files are kept in memory as ‘dumps or (where the PC has entered hibernation), as ‘hibernation’ files.

These temporary files allow access to the key used to secure the volumes if the target PC is discovered in its powered state or in a state of hibernation. Files can also be retrieved from a system that has been turned off as long as the PC entered hibernation while the volume was open prior to being powered down.

In summary, files encrypted with BitLocker, PGP and Truecrypt are safe from this product as long as volumes are opened or mounted and then closed and demounted in an orderly way; doing this destroys the insecure memory dump. For extra safety, hibernation should be disabled.

For the record, ElcomSoft doesn’t explain in detail how it finds and analyses the memory dumps used to retrieve the encryption key, although the company does admit the technique – specifically via FireWire - isn’t particularly new, just infrequently discussed.

“The new product includes algorithms allowing us to analyze dumps of computers’ volatile memory, locating areas that contain the decryption keys,” said ElcomSoft’s CEO, Vladimir Katalov, in a blog on the new software.

“Sometimes the keys are discovered by analyzing byte sequences, and sometimes by examining crypto containers’ internal structures. When searching for PGP keys, the user can significantly speed up the process if the exact encryption algorithm is known.”

Given that the software costs $299 (around £190) a license, its capabilities are likely to appeal to professional forensic analysts working for police forces. Such individuals need a means of accessing encrypted data without altering the information in a way that would cause problems in subsequent prosecutions.

Elcomsoft has a long track record of picking up on the weaknesses in encryption and other security systems, including the iPhone, BlackBerry’s data archive, and even Canon’s digital camera image verification system.