Changed retry count for RDRAND and RDSEED. RDSEED appears to fail to fulfill requests at about 6 to 8 times the rate of RDRAND.

1 files changed, 11 insertions, 6 deletions

diff --git a/rdrand.h b/rdrand.h
index fc2b77b7..6f4901be 100644
--- a/rdrand.h
+++ b/rdrand.h
@@ -1,8 +1,7 @@
 // rdrand.h - written and placed in public domain by Jeffrey Walton and Uri Blumenthal.

 //            Copyright assigned to Crypto++ project.

 

-//! \file

-//! \headerfile rdrand.h

+//! \file rdrand.h

 //! \brief Classes for RDRAND and RDSEED

 

 #ifndef CRYPTOPP_RDRAND_H

@@ -15,8 +14,8 @@
 //   indirectly uses CRYPTOPP_BOOL_{X86|X32|X64} (via CRYPTOPP_CPUID_AVAILABLE)

 //   to select an implementation or "throw NotImplemented". At runtime, the

 //   class uses the result of CPUID to determine if RDRAND or RDSEED are

-//   available. A lazy throw strategy is used in case the CPU does not support

-//   the instruction. I.e., the throw is deferred until GenerateBlock() is called.

+//   available. If not available, a lazy throw strategy is used. I.e., the

+//   throw is deferred until GenerateBlock() is called.

 

 // Microsoft added RDRAND in August 2012, VS2012. GCC added RDRAND in December 2010, GCC 4.6.

 // Clang added RDRAND in July 2012, Clang 3.2. Intel added RDRAND in September 2011, ICC 12.1.

@@ -43,7 +42,10 @@ public:
 	//! \param retries the number of retries for failed calls to the hardware

 	//! \details RDRAND() constructs a generator with a maximum number of retires

 	//!   for failed generation attempts.

-	RDRAND(unsigned int retries = 8) : m_retries(retries) {}

+	//! \details Empirical testing under a 6th generaton i7 (6200U) shows RDSEED fails

+	//!   to fulfill requests at about 6 to 8 times the rate of RDRAND. The default

+	//!   retries reflects the difference.

+	RDRAND(unsigned int retries = 12) : m_retries(retries) {}

 	

 	virtual ~RDRAND() {}

 	

@@ -122,7 +124,10 @@ public:
 	//! \param retries the number of retries for failed calls to the hardware

 	//! \details RDSEED() constructs a generator with a maximum number of retires

 	//!   for failed generation attempts.

-	RDSEED(unsigned int retries = 8) : m_retries(retries) {}

+	//! \details Empirical testing under a 6th generaton i7 (6200U) shows RDSEED fails

+	//!   to fulfill requests at about 6 to 8 times the rate of RDRAND. The default

+	//!   retries reflects the difference.

+	RDSEED(unsigned int retries = 64) : m_retries(retries) {}

 	

 	virtual ~RDSEED() {}