[LUG.ro] Vulnerabilidad en encriptación de discos

[Patricio Keilty]

Hola,
les paso un intersante estudio sobre ataques de booteo en frio para
obtener claves de encriptación en DRAM.

http://citp.princeton.edu/memory/

De las preguntas frecuentes:

Q. What encryption software is vulnerable to these attacks?
 A. We have demonstrated practical attacks against several popular
disk encryption systems: BitLocker (a feature of Windows Vista),
FileVault (a feature of Mac OS X), dm-crypt (a feature of Linux), and
TrueCrypt (a third-party application for Windows, Linux, and Mac OS
X). Since these problems result from common design limitations of
these systems rather than specific bugs, most similar disk encryption
applications, including many running on servers, are probably also
vulnerable.

Q. What can users do to protect themselves?
 A. The most effective way for users to protect themselves is to fully
shut down their computers several minutes before any situation in
which the computers' physical security could be compromised. On most
systems, locking the screen or switching to "suspend" or "hibernate"
mode does not provide adequate protection. (Exceptions exist; some
systems may not be protected even when powered off. Check with the
developer of your disk encryption software for further guidance.)

Q. Don't we already know that someone with physical access to my
computer can steal my data?
 A. The main purpose of disk encryption is to prevent someone who has
physical access to your computer from accessing your data without your
key or password. People commonly use these tools with the assumption
that they provide substantial protection should their computers be
lost or stolen. Unfortunately, we demonstrate that existing disk
encryption systems rely on assumptions about computer memory that make
them vulnerable to attack under certain common circumstances.

 Q. Isn't this the same as burn-in effects noticed by Gutmann? Can't
encryption programs rotate keys to get around this?
 A. Gutmann notes that data written to RAM for extended periods may
become "burned in," allowing it to be easily recovered later. We
describe a different effect: data written even momentarily to RAM
persists for a non-trivial period of time. We exclusively rely on the
latter effect to recover data. This allows us to recover keys even if,
following Gutmann's advice, those keys are stored only briefly at any
single location within RAM.

Q. Isn't your attack difficult to carry out? Don't you need materials
like liquid nitrogen?
 A. We found that information in most computers' RAMs will persist
from several seconds to a minute even at room temperature. We also
found a cheap and widely available product — "canned air" spray
dusters — can be used to produce temperatures cold enough to make RAM
contents last for a long time even when the memory chips are
physically removed from the computer. The other components of our
attack are easy to automate and require nothing more unusual than a
laptop and an Ethernet cable, or a USB Flash drive. With only these
supplies, someone could carry out our attacks against a target
computer in a matter of minutes.

Parece que para proteger las laptops vamos a tener que extraerles los
memory chips :P

saludos,
--p