Module randombytes 

randombytes equivalent (docs/dstu-crypto-project.md “Mapping onto the libsodium API”, docs/TASKS.md T-72, docs/DECISIONS.md D-48) - not a DSTU primitive. Wraps the OS CSPRNG (getrandom), same as libsodium’s own randombytes_buf does.

hazmat primitives never generate their own randomness (D-09 - callers supply everything). getrandom fails to compile outright on an unrecognized bare-metal target (docs/DECISIONS.md D-04’s addendum) unless a backend is selected - so pulling it in is opt-in, never bundled into a bare no_std build with no way to say no. Two ways to opt in: the std feature (assumes a real OS, getrandom picks its OS backend automatically), or the narrower getrandom feature (docs/TASKS.md T-123, docs/DECISIONS.md D-74) for no_std targets - an embedded caller who has configured one of getrandom’s own non-OS backends (most commonly custom, via --cfg getrandom_backend="custom" plus their own extern "Rust" fn __getrandom_v03_custom; see https://docs.rs/getrandom/latest/getrandom/#custom-backend) can enable this feature alone and use randombytes_buf without pulling in std/alloc at all. This crate does not implement its own pluggable-backend registry - getrandom 0.3 already is the mechanism libsodium’s randombytes_set_implementation() plays the same role for (capability parity, not mechanism parity: getrandom’s selection is a compile-time/link-time choice the final binary makes, not a runtime-swappable function pointer) - building a second one here would duplicate an already-established primitive docs/DECISIONS.md D-03/D-04 already rejected doing for the RNG itself.

Structs

RandomError

The OS CSPRNG failed to produce randomness (e.g. the platform’s entropy source is transiently unavailable). See getrandom::Error for the possible underlying causes.

Functions

randombytes_buf

Fills buf with cryptographically secure random bytes from the OS CSPRNG.