96 lines
3.8 KiB
C++
96 lines
3.8 KiB
C++
// darn.h - written and placed in public domain by Jeffrey Walton
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// DARN requires POWER9/ISA 3.0.
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// At the moment only GCC 7.0 (and above) seems to support __builtin_darn()
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// and __builtin_darn_32(). However, GCC generates incorrect code. Clang 7.0
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// does not provide them, but it does support assembly instructions. XLC is
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// unknown, but there are no hits when searching IBM's site. To cover more
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// platforms we provide GCC inline assembly like we do with RDRAND and RDSEED.
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// Platforms that don't support GCC inline assembly or the builtin will fail
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// to compile. Also see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91481 and
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// https://gcc.gnu.org/onlinedocs/gcc/Basic-PowerPC-Built-in-Functions-Available-on-ISA-3_002e0.html
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/// \file darn.h
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/// \brief Classes for DARN RNG
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/// \sa <A HREF="https://openpowerfoundation.org/?resource_lib=power-isa-version-3-0">Power
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/// ISA Version 3.0B</A>
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/// \since Crypto++ 8.0
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#ifndef CRYPTOPP_DARN_H
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#define CRYPTOPP_DARN_H
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#include "cryptlib.h"
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NAMESPACE_BEGIN(CryptoPP)
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/// \brief Exception thrown when a DARN generator encounters
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/// a generator related error.
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/// \since Crypto++ 8.0
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class DARN_Err : public Exception
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{
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public:
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DARN_Err(const std::string &operation)
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: Exception(OTHER_ERROR, "DARN: " + operation + " operation failed") {}
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};
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/// \brief Hardware generated random numbers using DARN instruction
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/// \details DARN() provides access to Power9's random number generator. The
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/// Crypto++ implementation provides conditioned random numbers from the
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/// generator as opposed to raw random numbers. According to Power ISA 3.0B
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/// manual, a conditioned random number has been processed by hardware to
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/// reduce bias. A raw random number is unconditioned noise source output.
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/// \details According to Power ISA 3.0B manual, the random number generator
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/// provided by the <tt>darn</tt> instruction is NIST SP800-90B and SP800-90C
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/// compliant to the extent possible given the completeness of the standards
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/// at the time the hardware is designed. The random number generator provides
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/// a minimum of 0.5 bits of entropy per bit.
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/// \par Wraps
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/// darn instruction
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/// \sa <A HREF="https://openpowerfoundation.org/?resource_lib=power-isa-version-3-0">Power
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/// ISA Version 3.0B</A>, MaurerRandomnessTest() for random bit generators
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/// \since Crypto++ 8.0
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class DARN : public RandomNumberGenerator
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{
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public:
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CRYPTOPP_STATIC_CONSTEXPR const char* StaticAlgorithmName() { return "DARN"; }
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virtual ~DARN() {}
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/// \brief Construct a DARN generator
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/// \throw DARN_Err if the random number generator is not available
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DARN();
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/// \brief Generate random array of bytes
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/// \param output the byte buffer
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/// \param size the length of the buffer, in bytes
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virtual void GenerateBlock(byte *output, size_t size);
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/// \brief Generate and discard n bytes
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/// \param n the number of bytes to generate and discard
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/// \details the RDSEED generator discards words, not bytes. If n is
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/// not a multiple of a machine word, then it is rounded up to
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/// that size.
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virtual void DiscardBytes(size_t n);
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/// \brief Update RNG state with additional unpredictable values
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/// \param input unused
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/// \param length unused
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/// \details The operation is a nop for this generator.
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virtual void IncorporateEntropy(const byte *input, size_t length)
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{
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// Override to avoid the base class' throw.
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CRYPTOPP_UNUSED(input); CRYPTOPP_UNUSED(length);
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}
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std::string AlgorithmProvider() const {
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return "Power9";
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}
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private:
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SecBlock<byte, AllocatorWithCleanup<byte, true> > m_temp;
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};
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NAMESPACE_END
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#endif // CRYPTOPP_DARN_H
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