Hiya,
On 02/17/2012 11:11 PM, Adam Back wrote:
I dont think this is going to be very robust because the fact that the
entropy seeding is so bad that some implementations are generating
literally the same p value (but seemingly different q values) I would
think you could view the fact that this can be
detected and efficiently exploited via batch GCD as an indication of an even
bigger problem.
Namely if the seeding is that bad you could outright compute all possible
values of p even for cases where p was not shared, by running through the
evidently small by cryptographic standards number of possible PRNG states...
Then you might be looking at more than 1% or whatever the number is that
literally collide in specific p value. Assuming p is more vulnerable than
q, you could then use the same batch GCD to test.
Sure. But wouldn't this protocol still help then? Assuming that
protocol clients don't ignore the known-bad answers, they'd
hopefully iterate until they get a not-known-bad key one way or
another.
I think so, but maybe you're seeing something I'm not.
Something not that clear in the -00 is that the responder here
can supply random bits as a side effect of answering the
query. (The -01 will make this clearer when its ready.)
S.
Adam
On 16 February 2012 14:12, Stephen Farrell<[email protected]> wrote:
Dunno if anyone else thinks this might be interesting
but I do:-)
So I sketched out an initial idea for how it might fit
in here. [1]
Comments welcome.
S.
[1] http://www.ietf.org/id/draft-farrell-kc-00.txt
On 02/15/2012 07:17 PM, Stephen Farrell wrote:
Hiya,
I guess the recent publications about common factors [1,2]
are something else that this group might want to consider.
I wonder if an rsa modulus checker protocol might help or
something. Not sure if that's something that could be run
quickly enough though, other than for the straight
duplicates or dumbass things with small factors you should
spot yourself. Anyone know?
Or maybe you could register your public key and get a
nonce, then come back periodically to see if any problems
have been detected for your key.
And yes, better prngs are needed, but there'll probably
always be bad ones out there.
S.
[1] http://eprint.iacr.org/2012/064
[2]
http://it.slashdot.org/story/12/02/15/1540212/factorable-keys-twice-as-many-but-half-as-bad
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