Re: max length of randomLen for C_GenerateRandom

Hi


> You want to marry your smart card as a source of entropy to a DBRG and
> reseed the DBRG from the smart card fairly often.   See NIST SP800-90A for
> the general form for a DBRG.
>

Since 2007 and 2013, the SP800-90A has been criticized ;)
All the controversy aside, the simultaneous use is a good idea, though.


> Alternately, you can use multiple sources of entropy - a smart card, a
> TPM, one of the TRNGs from above and use them to seed the DBRG.  That way
> you're not dependent on any of these being "trusted".  Simplest way to do
> this is XOR the N streams of TRNG data together to provide the seed and
> reseed data.  Oh yeah - most modern Intel motherboards and processors
> support the RDRAND and RDSEED instructions and there is software to expose
> those for use. (https://software.intel.com/en-us/articles/intel-digital-
> random-number-generator-drng-software-implementation-guide)
>
> As long as your TRNG can keep up with the reseed schedule, you can get a
> *lot* of bits out of the DRBG.
>

I'll dig into that some more


> WRT to the smart card, my guess is there is a TRNG backing a DBRG of some
> sort.
>

Again, this may be checked if I have the source code of the PKCS11 driver,
yes?

I wouldn't trust a generic PKCS11 driver to do what you want.
>

Do you mean "generic" as in a driver not provided by the vendor itself?
(i.e. OpenSC or Charismatics)

Cheers

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