Re: [Cfrg] considering new topics for CFRG

Henrick Hellström <henrick@streamsec.se> Sat, 04 January 2014 03:02 UTC

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Subject: Re: [Cfrg] considering new topics for CFRG
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On 2014-01-04 03:41, David Wagner wrote:
> Back in 2005, David Molnar, Matt Piotrowski, David Schultz,
> and I proposed a simple method for testing for side channel
> vulnerabilities.  You instrument the program with gcov, then run it
> many times with many different randomly chosen keys (but with
> all other inputs held fixed), using gcov to gather a set of statement
> coverage statistics separately for each different key.  Then, you
> look at the statement coverage statistics that gcov produced.
> If you find any line in the code that was executed more times
> for some keys than for others, you have found a potential
> side channel vulnerability, as you've found some evidence that
> whether or not that line will be executed depends upon the value
> of the key.

This method will not detect timing differences caused by cache misses. 
(Think table look-ups, or branch-less pointer swapping.)