random.cpp File Reference

#include <bitcoin-build-config.h>
#include <random.h>
#include <compat/compat.h>
#include <compat/cpuid.h>
#include <crypto/chacha20.h>
#include <crypto/sha256.h>
#include <crypto/sha512.h>
#include <randomenv.h>
#include <span.h>
#include <support/allocators/secure.h>
#include <support/cleanse.h>
#include <sync.h>
#include <util/log.h>
#include <util/time.h>
#include <array>
#include <cmath>
#include <cstdlib>
#include <optional>
#include <thread>
#include <fcntl.h>
#include <sys/time.h>

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Functions
void	MakeRandDeterministicDANGEROUS (const uint256 &seed) noexcept
	Internal function to set g_determinstic_rng.
void	GetRandBytes (std::span< unsigned char > bytes) noexcept
	Generate random data via the internal PRNG.
void	GetStrongRandBytes (std::span< unsigned char > bytes) noexcept
	Gather entropy from various sources, feed it into the internal PRNG, and generate random data using it.
void	RandAddPeriodic () noexcept
	Gather entropy from various expensive sources, and feed them to the PRNG state.
void	RandAddEvent (const uint32_t event_info) noexcept
	Gathers entropy from the low bits of the time at which events occur.
bool	Random_SanityCheck ()
	Check that OS randomness is available and returning the requested number of bytes.
void	RandomInit ()
double	MakeExponentiallyDistributed (uint64_t uniform) noexcept
	Given a uniformly random uint64_t, return an exponentially distributed double with mean 1.

Variables
std::atomic< bool >	g_used_g_prng {false}
static constexpr std::array< std::byte, ChaCha20::KEYLEN >	ZERO_KEY {}

Function Documentation

GetRandBytes()

void GetRandBytes ( std::span< unsigned char > bytes )

noexcept

Generate random data via the internal PRNG.

These functions are designed to be fast (sub microsecond), but do not necessarily meaningfully add entropy to the PRNG state.

In test mode (see SeedRandomForTest in src/test/util/random.h), the normal PRNG state is bypassed, and a deterministic, seeded, PRNG is used instead.

Thread-safe.

Definition at line 601 of file random.cpp.

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GetStrongRandBytes()

void GetStrongRandBytes ( std::span< unsigned char > bytes )

noexcept

Gather entropy from various sources, feed it into the internal PRNG, and generate random data using it.

This function will cause failure whenever the OS RNG fails.

The normal PRNG is never bypassed here, even in test mode.

Thread-safe.

Definition at line 607 of file random.cpp.

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MakeExponentiallyDistributed()

double MakeExponentiallyDistributed ( uint64_t uniform )

noexcept

Given a uniformly random uint64_t, return an exponentially distributed double with mean 1.

Definition at line 704 of file random.cpp.

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MakeRandDeterministicDANGEROUS()

void MakeRandDeterministicDANGEROUS ( const uint256 & seed )

noexcept

Internal function to set g_determinstic_rng.

Only accessed from tests.

Definition at line 595 of file random.cpp.

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RandAddEvent()

void RandAddEvent ( uint32_t event_info )

noexcept

Gathers entropy from the low bits of the time at which events occur.

Should be called with a uint32_t describing the event at the time an event occurs.

Thread-safe.

Definition at line 617 of file random.cpp.

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RandAddPeriodic()

void RandAddPeriodic ( )

noexcept

Gather entropy from various expensive sources, and feed them to the PRNG state.

Thread-safe.

Definition at line 612 of file random.cpp.

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Random_SanityCheck()

bool Random_SanityCheck

(

)

Check that OS randomness is available and returning the requested number of bytes.

Definition at line 641 of file random.cpp.

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RandomInit()

void RandomInit

(

)

Definition at line 696 of file random.cpp.

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Variable Documentation

g_used_g_prng

std::atomic<bool> g_used_g_prng {false}

Definition at line 599 of file random.cpp.

ZERO_KEY

std::array<std::byte, ChaCha20::KEYLEN> ZERO_KEY {}

staticconstexpr

Definition at line 687 of file random.cpp.