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Update comments for Intel RDRAND circuit and underflow

pull/200/head
Jeffrey Walton 2016-06-14 22:14:35 -04:00
parent 2efe26a418
commit d3e566da61
1 changed files with 7 additions and 4 deletions
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11
rdrand.h
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@ -42,10 +42,13 @@ public:
//! \param retries the number of retries for failed calls to the hardware //! \param retries the number of retries for failed calls to the hardware
//! \details RDRAND() constructs a generator with a maximum number of retires //! \details RDRAND() constructs a generator with a maximum number of retires
//! for failed generation attempts. //! for failed generation attempts.
//! \details Empirical testing under a 6th generaton i7 (6200U) shows RDSEED fails //! \details According to DJ of Intel, the Intel RDRAND circuit does not underflow.
//! to fulfill requests at about 6 to 8 times the rate of RDRAND. The default //! If it did hypothetically underflow, then it would return 0 for the random value.
//! retries reflects the difference. //! Its not clear what AMD's behavior will be, and what the returned value will be if
RDRAND(unsigned int retries = 12) : m_retries(retries) {} //! underflow occurs.
//! Also see <A HREF="https://lists.randombit.net/pipermail/cryptography/2016-June/007702.html">RDRAND
//! not really random with Oracle Studio 12.3 + patches</A>
RDRAND(unsigned int retries = 4) : m_retries(retries) {}
virtual ~RDRAND() {} virtual ~RDRAND() {}