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// rdrand.h - written and placed in public domain by Jeffrey Walton and Uri Blumenthal.
/// \file rdrand.h
/// \brief Classes for RDRAND and RDSEED
/// \since Crypto++ 5.6.3
#ifndef CRYPTOPP_RDRAND_H
#define CRYPTOPP_RDRAND_H
#include "cryptlib.h"
// This class file provides both RDRAND and RDSEED. They were added at
// Crypto++ 5.6.3. At compile time, it uses CRYPTOPP_BOOL_{X86|X32|X64}
// to select an implementation or "throw NotImplemented". At runtime the
// constructor will throw RDRAND_Err or RDSEED_Err if a generator is
// is not available.
// The original classes accepted a retry count. Retries were superflous for
// RDRAND, and RDSEED encountered a failure about 1 in 256 bytes depending
// on the processor. Retries were removed at Crypto++ 6.0 because
// GenerateBlock unconditionally retries and always fulfills the request.
// Throughput varies wildly depending on processor and manufacturer. A Core i5 or
// Core i7 RDRAND can generate at over 200 MiB/s. Its below the theroetical
// maximum, but it takes about 5 instructions to generate, retry and store a
// result. A low-end Celeron may perform RDRAND at about 7 MiB/s. RDSEED
// performs at about 1/4 to 1/2 the rate of RDRAND. AMD RDRAND performed poorly
// during testing with Athlon X4 845. The Bulldozer v4 only performed at 1 MiB/s.
// Microsoft added RDRAND in August 2012, VS2012; RDSEED in October 2013, VS2013.
// GCC added RDRAND in December 2010, GCC 4.6. LLVM added RDRAND in July 2012,
// Clang 3.2. Intel added RDRAND in September 2011, ICC 12.1.
NAMESPACE_BEGIN(CryptoPP)
/// \brief Exception thrown when a RDRAND generator encounters
/// a generator related error.
/// \since Crypto++ 5.6.3
class RDRAND_Err : public Exception
{
public:
RDRAND_Err(const std::string &operation)
: Exception(OTHER_ERROR, "RDRAND: " + operation + " operation failed") {}
};
/// \brief Hardware generated random numbers using RDRAND instruction
/// \sa MaurerRandomnessTest() for random bit generators
/// \since Crypto++ 5.6.3
class RDRAND : public RandomNumberGenerator
{
public:
CRYPTOPP_STATIC_CONSTEXPR const char* StaticAlgorithmName() { return "RDRAND"; }
virtual ~RDRAND() {}
/// \brief Construct a RDRAND generator
/// \details According to DJ of Intel, the Intel RDRAND circuit does not underflow.
/// If it did hypothetically underflow, then it would return 0 for the random value.
/// AMD's RDRAND implementation appears to provide the same behavior.
/// \throws RDRAND_Err if the random number generator is not available
RDRAND();
/// \brief Generate random array of bytes
/// \param output the byte buffer
/// \param size the length of the buffer, in bytes
virtual void GenerateBlock(byte *output, size_t size);
/// \brief Generate and discard n bytes
/// \param n the number of bytes to generate and discard
/// \details the RDSEED generator discards words, not bytes. If n is
/// not a multiple of a machine word, then it is rounded up to
/// that size.
virtual void DiscardBytes(size_t n);
/// \brief Update RNG state with additional unpredictable values
/// \param input unused
/// \param length unused
/// \details The operation is a nop for this generator.
virtual void IncorporateEntropy(const byte *input, size_t length)
{
// Override to avoid the base class' throw.
CRYPTOPP_UNUSED(input); CRYPTOPP_UNUSED(length);
}
};
/// \brief Exception thrown when a RDSEED generator encounters
/// a generator related error.
/// \since Crypto++ 5.6.3
class RDSEED_Err : public Exception
{
public:
RDSEED_Err(const std::string &operation)
: Exception(OTHER_ERROR, "RDSEED: " + operation + " operation failed") {}
};
/// \brief Hardware generated random numbers using RDSEED instruction
/// \sa MaurerRandomnessTest() for random bit generators
/// \since Crypto++ 5.6.3
class RDSEED : public RandomNumberGenerator
{
public:
CRYPTOPP_STATIC_CONSTEXPR const char* StaticAlgorithmName() { return "RDSEED"; }
virtual ~RDSEED() {}
/// \brief Construct a RDSEED generator
/// \details Empirical testing under a 6th generaton i7 (6200U) shows RDSEED fails
/// to fulfill requests at about once every for every 256 bytes requested.
/// The generator runs about 4 times slower than RDRAND.
/// \throws RDSEED_Err if the random number generator is not available
RDSEED();
/// \brief Generate random array of bytes
/// \param output the byte buffer
/// \param size the length of the buffer, in bytes
virtual void GenerateBlock(byte *output, size_t size);
/// \brief Generate and discard n bytes
/// \param n the number of bytes to generate and discard
/// \details the RDSEED generator discards words, not bytes. If n is
/// not a multiple of a machine word, then it is rounded up to
/// that size.
virtual void DiscardBytes(size_t n);
/// \brief Update RNG state with additional unpredictable values
/// \param input unused
/// \param length unused
/// \details The operation is a nop for this generator.
virtual void IncorporateEntropy(const byte *input, size_t length)
{
// Override to avoid the base class' throw.
CRYPTOPP_UNUSED(input); CRYPTOPP_UNUSED(length);
}
};
NAMESPACE_END
#endif // CRYPTOPP_RDRAND_H
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