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Mixing static and changing environment data into randomness

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1// Copyright (c) 2009-2010 Satoshi Nakamoto
2// Copyright (c) 2009-present The Bitcoin Core developers
3// Distributed under the MIT software license, see the accompanying
4// file COPYING or http://www.opensource.org/licenses/mit-license.php.
5
6#ifndef BITCOIN_RANDOMENV_H
7#define BITCOIN_RANDOMENV_H
8
9#include <crypto/sha512.h>
10
11/** Gather non-cryptographic environment data that changes over time. */
12void RandAddDynamicEnv(CSHA512& hasher);
13
14/** Gather non-cryptographic environment data that does not change over time. */
15void RandAddStaticEnv(CSHA512& hasher);
16
17#endif // BITCOIN_RANDOMENV_H
18

FILE GUIDE · KEY SECTIONS

Mixing static and changing environment data into randomness

Two declarations add noncryptographic environment observations to a SHA512 hasher used by the wider random subsystem.

Line 12 ↗

Dynamic observations can supplement a pool

The dynamic helper gathers information that changes over time. Accepting a hasher lets the implementation mix observations into a caller’s state. The header explicitly calls the data noncryptographic, so it must not be presented as a standalone secure random-number generator.

Line 15 ↗

Static observations have a different role

Static environment data changes less often and has its own helper. Neither function returns random bytes or promises a particular amount of entropy. Key generation must follow the full random subsystem’s secure interfaces rather than hashing a few predictable environmental values.

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