[FDE] Data at Rest, Data in Transit, and Data in Use

[Michael Jardine]

   Simply put, as processing power increases to decrease the time to crack a
key, so can that same processing power be increased to strengthen the key
(or algorithm).  So unless something radically changes, the latter will
always remain ahead of the former. And yes, you will have to 'roll forward.'
The same applies to methods and media for backing up and protecting digital
data that you do not want encrypted.
   
   
   Regards,
   Michael Jardine
   SECUDE IT Security
   
   
   -----Original Message-----
From: fde-bounces at www.xml-dev.com [mailto:fde-bounces at www.xml-dev.com] On
Behalf Of Allen
Sent: Monday, July 23, 2007 8:44 PM
To: fde at www.xml-dev.com
Subject: Re: [FDE] Data at Rest, Data in Transit, and Data in Use
   
   Michael Jardine wrote:
   >    Pete,
   >    
   >    A brute force attack on an AES-256 encrypted drive that has a STRONG
   > "Password" or Key would take years.  Of course, no one could prevent a
   > brute-force attack if the attacker gained physical access to the drive
in
   > question - however if the users password (and thus the key) isn't
12345678
   > or some other Dilbertian string, then it's realistically impossible to
   > retrieve the key in a reasonable time frame.
   
   I'm not raising objections just to be querulous, but rather to 
   think ahead for possible corner cases which perhaps should be 
   considered when developing policies.
   
   Okay, we all know Moore Law, right? And we all know that the 
   needed lifespan for the encryption is based on the value of the 
   data and the time frame for required protection, Right?
   
   For discussion's sake let's assume that HD life is not an issue 
   as bit copies will be made and duplicated as long as is needed to 
   brute force the key. So what kind of data requires long term 
   protection? Obviously plans for attacking someone need to only 
   last until after the attack. The same can be said about almost 
   all business data, be it credit card, billing, marketing, etc. 
   Yes, these might require 20, even 50 year containment, but that 
   is still relatively short.
   
   What might need protection for more than 100 years is your DNA 
   data. These days babies are checked at birth and the code could 
   reveal information about you - susceptibility to disease and such 
   - that might be used covertly to discriminate against you in one 
   way or another. Given that I now regularly see obituaries for 
   people over 100. Given the propensity to sue, in the US, at the 
   drop of an imagined injury or defect in disclosure this might 
   mean that you would have to protect DNA data for the lifespan of 
   a person plus sometime afterward to prevent suits against the 
   estate of the person. Add to this that estates seem to last well 
   beyond the natural lifespan in some cases - the current minor 
   flap around Kerouac or how the James Joyce and the Bertholt 
   Brecht estates still attempt to control the use of their literary 
   works are good examples - and the ability of lawyers in the US to 
   create lawsuits I can well imagine that 150 years is not totally 
   unreasonable.
   
   Okay, what metric do we apply as a measuring stick for brute 
   force resistance? Let's use the creation of collisions with one 
   of the hash functions as a starting point. The figure as I recall 
     was a space of 2^59 taking 80,000 CPU hours to complete. The 
   machine was a 256 CPU Itanium super computer in 2005. This works 
   to to less than 14 days. Given that the same machine could be 
   constructed with almost 4 times as much power today at a lower 
   cost, how long will it be before it is realistic to crack 256 
   bits of key space with machines that could be created in 50 years 
   by people with even modest budgets?
   
   Even assuming that Moore's law flattens, the price of CPU 
   horsepower does not decline at the rate it has in the last 
   several years, no new time v. effort approaches are thought of or 
   other algorithmic attacks created, it is highly unlikely that the 
   current AES-256 standard would last that long. Given this there 
   are only two ways to protect your data, keep rolling the 
   encryption standard and pray that a copy with a weaker key does 
   not exist, or destruction of the data. Given human fallibility I 
   think the choice is obvious - destruction once the need for 
   access to the data has ended no matter how long that is.
   
   Yes, this is a corner case that is highly unlikely to ever 
   happen, but things happen. Look at D.B. Cooper and the 727 exit 
   X. Who would have ever thought you could parachute from a jet and 
   survive? While we don't know if he did survive, we do know that 
   five months later Richard Floyd McCoy, Jr., using the name James 
   Johnson, hijacked United Airlines Flight 855 and also parachuted 
   into the night from its rear stairs with half a million dollars. 
   Yes, McCoy was caught and convicted in federal court in June of 
   1972 in Salt Lake City, Utah.
   
   So you can see there are more possibilities than we have the 
   vision to foresee, so I suggest that we just destroy the data 
   *and* the key.
   
   
   Best,
   
   Allen
   
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