Crate arkhe_rand 

BLAKE3-keyed PRNG with split() determinism — Lemire unbiased range + Fisher-Yates shuffle. Shell-side use (kernel/runtime forbids RNG for deterministic replay).

Layer scope

arkhe-rand is an L3 Library tier crate per the ArkheForge layer model (L0 Kernel / L1 Runtime Primitives / L2 Runtime Services / L3 Library / L4-L6 Shell). The kernel and forge runtime forbid RNG entirely to preserve deterministic WAL replay; this crate is consumed only by shell-side code (BBS, examples, downstream applications).

Cryptographic core

Each RngSource wraps a BLAKE3 XOF stream constructed via the KDF mode Hasher::new_derive_key("arkhe-rand stream v0.13").update(seed). The context string eliminates cross-domain seed collisions; the v0.13 tag is permanent under the project’s single-version pin so patch releases (0.13.x) preserve wire stability for stored seeds.

XOF reader monotonic property is inherited from the blake3 crate spec (audited via supply-chain/audits.toml [[audits.blake3]]).

API

• RngSource::from_seed / RngSource::from_os_entropy / RngSource::split / RngSource::fill_bytes
• gen_range / gen_range_inclusive (Lemire nearlydivisionless)
• shuffle (Fisher-Yates, in-place)

Cross-platform determinism

Byte-to-integer conversions use explicit little-endian (u32::from_le_bytes / u64::from_le_bytes) regardless of host endianness, so x86_64 / aarch64 / wasm32 produce byte-identical streams from the same seed. CI enforces this via the golden-vector cross-compile comparison plus a repository self-grep that forbids native-endian conversion helpers in the source tree.

Structs

RngSource

BLAKE3-keyed PRNG.

Enums

RngError

Error returned by RngSource::from_os_entropy.

Traits

RandInt

Integer types accepted by gen_range / gen_range_inclusive.

Functions

gen_range

Sample a uniformly-random value from range ∈ [start, end).

gen_range_inclusive

Sample a uniformly-random value from range ∈ [start, end].

shuffle

In-place Fisher-Yates shuffle.