On Tue, 22 Nov 2011 16:16:21 -0000, Piotr Szturmaj <bncr...@jadamspam.pl>
wrote:
bcs wrote:
On 11/20/2011 08:10 AM, Piotr Szturmaj wrote:
bcs wrote:
On 11/04/2011 04:27 AM, Piotr Szturmaj wrote:
bcs wrote:
Are you re-implementing the function kernels your self or are you
using
an existing implementation? Given what I've heard about things like
side-channel attacks using processing times to recover keys, I'd
rather
not see Phobos use anything written by less than the best expert
available.
Until now, I implemented some hash functions. There are no branching
instructions in their transform() routines, so theoretically
processing
time is independent of the function input.
From my very incomplete memory I found the source I was looking for (I
googled for "aes interperative dance") here
http://www.moserware.com/2009/09/stick-figure-guide-to-advanced.html
Look for "Foot-Shooting Prevention Agreement" in one of the images
~20-25% of the way down.
tl;dr; It mentions "cache-based, timing, and other side channel
attacks". Unless you can explain to me what those are, in painful
detail, I don't think we should trust you to avoid them. Get a good
vetted C implementation and wrap it with a nice D API and call it a
day.
>
Sorry for late answer.
Np, but I still have a number of concerns:
What is the advantage to implementing the kernels of any of these
functions in D? Will the code be faster? Smaller? More secure? More
maintainable? (On the other hand, the value of doing the API code in D
goes with no debate.)
The first advantage is that Phobos will be independent of any crypto
libraries. The second one is that there will be no licensing issues. All
crypto code will be under Boost license like the rest of Phobos.
Ultimately I think it comes down to the question of whether we want/expect
to have native D implementations of things, or whether certain
projects/libraries will always be too large to maintain in D. The answer
to that, comes down to whether we think D will gain a sufficient user base
to include enough people able to produce and maintain those libraries, or
.. whether D will gain sufficient importance that existing developers in
those libraries produce D bindings themselves.
Under the assumption that D will gain sufficient traction it makes sense
to start implementing what we can in D, now. At the same time, in order
to gain that traction D needs bindings to existing libraries. The latter
is probably a slightly higher priority at present, but it's not a reason
not to develop native D implementations at the same time.
If we're lucky having initially incomplete native D implementations will
actually encourage people with those skills to contribute to D, as there
is a certain sort of satisfaction in doing so.
How many people in the D community have the experience and know-how to
review the security of an implementation? If there are less than 2 or 3
people who can do that, can we afford to include native kernels? We
can't have just one and if we have only two and one leaves for some
reason the code becomes un-maintainable for lack of a reviewer. *I*
wouldn't be comfortable with less than about 4-5.
I know Regan Heath who wrote some crypto code for Tango. Also, I suspect
that D _will_ gain more (crypto) contributors, especially after joining
GCC.
I wrote those as a crypto novice and haven't had any cause to advance
since then. There are some obvious things to watch out for, for example
the hashing routines should not make copies of the input data, or if they
do they should 'scrub' that memory clean afterwards. But, that's the
limit of my knowledge, there are bound to be more advanced problems and
solutions that I'm simply not aware of.
Regan
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