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    <div class="moz-cite-prefix">On 4/21/2017 8:41 AM, Florent wrote:<br>
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            <div>Hi</div>
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              <div bgcolor="#FFFFFF">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.<br>
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            <div>Since 2007 and 2013, the SP800-90A has been criticized
              ;)</div>
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    <br>
    Actually - its just the Dual EC mode that was criticized.   AFAICT,
    the remaining modes are as secure as the underlying PRF.<br>
    <br>
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            <div>All the controversy aside, the simultaneous use is a
              good idea, though.</div>
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              <div bgcolor="#FFFFFF">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.
                (<a moz-do-not-send="true"
                  class="gmail-m_-63490650965874880moz-txt-link-freetext"
href="https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide"
                  target="_blank">https://software.intel.com/<wbr>en-us/articles/intel-digital-<wbr>random-number-generator-drng-<wbr>software-implementation-guide</a>)<br>
                <br>
                As long as your TRNG can keep up with the reseed
                schedule, you can get a *lot* of bits out of the DRBG.<br>
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            <div>I'll dig into that some more</div>
            <div> <br>
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              <div bgcolor="#FFFFFF">WRT to the smart card, my guess is
                there is a TRNG backing a DBRG of some sort. <br>
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            <div>Again, this may be checked if I have the source code of
              the PKCS11 driver, yes?  <br>
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    <br>
    No - I've got the unredacted data sheets for the smart cards and
    they don't go any deeper than AIS31 compliant RNG. The PKCS11 driver
    has nothing to do with this. From conversations I had on the show
    floor at RSA many years ago, I believe there's some sort of noisy
    diode or some what as an entropy source, but I wouldn't make a bet
    on that belief.<br>
    <br>
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              <div bgcolor="#FFFFFF">I wouldn't trust a generic PKCS11
                driver to do what you want.<br>
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            <div>Do you mean "generic" as in a driver not provided by
              the vendor itself? (i.e. OpenSC or Charismatics) <br>
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    <br>
    Sorry - I actually should have said "random" as in any given PKCS11
    driver.  If you've got source you've got a better idea of what's
    happening, but even then if you don't have the detailed reality of
    the underlying HSM you may still be guessing wrong.<br>
    <br>
    Mike<br>
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            <div>Cheers</div>
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      <pre wrap="">_______________________________________________
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