On 6/8/2014 1:46 AM, Jeffrey Walton wrote:
OK, does the library provide the CRT solver (I don't believe so, but I
thought I would ask).
Few years ago, I needed such solver to convert from RSA SFM format
(n,e,d) to CRT representation. Obviously OpenSSL doesn't contain one so
I implemented it using OpenSSL routines and I released an Open Source
tool called RsaConverter that provide such functionality
(http://rsaconverter.sourceforge.net/).
You can have a look at the file librsaconverter.c from its source
(http://sourceforge.net/p/rsaconverter/code/HEAD/tree/Trunk/src/librsaconverter.c).
In your case, you can use the function SfmToCrt in order to compute the
CRT parameters, thus making RSA_check_key happy.
Before calling SfmToCrt, I advice to call CheckRsaSfmKey to verify that
the triplet (n,e,d) are valid for RSA otherwise SfmToCrt can't find the
CRT parameters (the algorithm is based on random search for a generator
that exists only for valid RSA parameters). In order to avoid infinite
loops, I implemented a configurable timeout.
Concerning its performance, the algorithm is fast : for RSA 2048, it
takes 250 ms on average on a Core i7-2600K and on the older Pentium III
M it takes 1 second on average.
I don't if there are many people who need use RSA SFM parameters but
having such conversion functionality inside OpenSSL can be interesting.
In such case, I can send a patch for it.
Cheers,
--
Mounir IDRASSI
IDRIX
http://www.idrix.fr
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