Module message_authenticator 

Message authentication with HMAC-like construction and replay attack prevention.

Provides production-quality message signing and verification using pure-Rust crypto primitives (FNV-1a based HMAC, xorshift64 PRNG) without any external crypto crates.

Design

• MessageAuthenticator manages a keystore of named AuthKey entries.
• Each key carries an AuthAlgorithm variant that controls how HMAC is computed.
• A ReplayWindow tracks recently seen nonces to block replay attacks.
• Policy flags (AuthPolicy) let callers enforce sequential nonces or key rotation.
• All significant events (sign, verify, error) are recorded in an internal audit log drainable via drain_events().

Collision notes (lib.rs re-export)

• fnv1a_64 / xorshift64 are already exported under ntm_ / smx_ / etc. aliases. The helpers in this module are re-exported as mau_fnv1a_64 and mau_xorshift64 to avoid collisions.
• No other types in this module collide with existing crate-root exports as of the time of writing (confirmed by grepping lib.rs for each name before creating this file).

Structs

AuthKey

A named secret key used for signing and verifying messages.

AuthStats

Cumulative counters collected by MessageAuthenticator.

MessageAuthenticator

Production-quality message authenticator with:

ReplayWindow

Sliding window of recently observed nonces used to detect replay attacks.

SignedMessage

A payload together with its authentication tag and metadata.

Enums

AuthAlgorithm

Authentication algorithm selection.

AuthError

All errors that can be returned by MessageAuthenticator.

AuthPolicy

Authentication enforcement policy.

Functions

fnv1a_64

FNV-1a 64-bit hash over data.

hmac_fnv64

HMAC-FNV64 simplified construction.

xorshift64

Xorshift-64 PRNG.