Support is provided on a best-effort bases only. No binding guarantees can be provided.
Rand provides the trait rand_core::CryptoRng aka rand::CryptoRng as a marker
trait. Generators implementing RngCore and CryptoRng, and given the
additional constraints that:
- Instances of seedable RNGs (those implementing
SeedableRng) are constructed with cryptographically secure seed values - The state (memory) of the RNG and its seed value are not be exposed
are expected to provide the following:
- An attacker can gain no advantage over chance (50% for each bit) in predicting the RNG output, even with full knowledge of all prior outputs.
For some RNGs, notably OsRng, ThreadRng and those wrapped by ReseedingRng,
we provide limited mitigations against side-channel attacks:
- After a process fork on Unix, there is an upper-bound on the number of bits output by the RNG before the processes diverge, after which outputs from each process's RNG are uncorrelated
- After the state (memory) of an RNG is leaked, there is an upper-bound on the number of bits of output by the RNG before prediction of output by an observer again becomes computationally-infeasible
Additionally, derivations from such an RNG (including the Rng trait,
implementations of the Distribution trait, and seq algorithms) should not
introduce significant bias other than that expected from the operation in
question (e.g. bias from a weighted distribution).
We will attempt to uphold these premises in the following crate versions, provided that only the latest patch version is used, and with potential exceptions for theoretical issues without a known exploit:
| Crate | Versions | Exceptions |
|---|---|---|
rand |
0.8 | |
rand |
0.7 | |
rand |
0.5, 0.6 | Jitter |
rand |
0.4 | Jitter, ISAAC |
rand_core |
0.2 - 0.6 | |
rand_chacha |
0.1 - 0.3 |
Explanation of exceptions:
- Jitter:
JitterRngis used as an entropy source when the primary source fails; this source may not be secure against side-channel attacks, see #699. - ISAAC: the ISAAC RNG used
to implement
thread_rngis difficult to analyse and thus cannot provide strong assertions of security.
In rand version 0.3 (0.3.18 and later), if OsRng fails, thread_rng is
seeded from the system time in an insecure manner.
To report a vulnerability, open a new issue. Once the issue is resolved, the vulnerability should be reported to RustSec.