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Opt-in acceleration availability contract

Status: the v0.24.30 contract remains the normative family-integration model. The v0.24.31 static authority API now implements ordinary low-level execution for five modern kernels under a specialized executable contract. The inventory's existing operational flags describe high-level family activation, not this new raw authority surface. Hosted selection starts at v0.24.32; family activation follows the release plan.

Independent status axes

Operational availability means first-party implementation, correctness and public package tests, exact platform authority, startup/continuing health, and the requested ordinary or hardened profile have passed their applicable gates. It does not require a third-party reviewer or a FIPS certificate. Neither a native benchmark, an independent review nor a FIPS claim can grant execution authority. Native observations remain scoped by source, compiler, CPU and OS; performance, independent verification and certificate-bound validation are separate observations, not interchangeable approvals.

The machine-readable inventory records eleven implemented kernels and nine families (29 algorithm identities, including the parameterized SHA-512/t family). Reserved AES/AVX-512/RVV entries in the older admission register are not implemented kernels. The register stays unchanged until each activation implementation passes its own review. Updating an inventory boolean alone must never activate a backend.

Selection and failure semantics

Request Before execution After an accelerated session begins
Portable Never selects or probes an accelerated route Remains portable
Prefer Exact available route, or explicitly reported portable fallback for unsupported/unavailable profile Authority loss or integrity failure is terminal; no silent fallback
Require Exact available route, otherwise typed rejection Authority loss or integrity failure is terminal; no silent fallback

A failed KAT or quarantined implementation is an integrity error, not an opportunity to retry a different backend. The first terminal error is sticky. Backend, algorithm (including SHA-512/t's t), profile and workload identities must survive streaming, finalization, output and reporting. Failed public-output operations preserve their destination; failed secret-output operations clear the entire secret destination. Streaming partial-output contracts must state what has already been released; they cannot retroactively retract output.

Future reports distinguish dedicated instructions, single-state SIMD, independent-message SIMD, scalar tails and host worker counts. Running portable code in multiple threads is not SIMD. Zero full blocks can legitimately perform no accelerated compression; reports must disclose actual work, never infer it from a selected feature. No-op, scalar-only and evidence-cfg-only implementations cannot satisfy an operational acceleration promise.

Authority and package boundaries

  • Default features stay empty/portable. Leaf CPU features are explicit, additive and non-authorizing. A feature does not establish CPU support.
  • Allocation-free static use needs the complete compiler target-feature bundle and a sound executable/platform contract. Every possible scheduled CPU/hart and the OS-managed register state must satisfy it. A safe caller-provided boolean, CPUID alone or a non-Send session is insufficient.
  • Hosted detection belongs in opt-in -std adapters, not the no_std leaf. Unknown OS/VM, migration or feature-state guarantees fail closed. AVX2 needs OSXSAVE/XCR0 XMM/YMM state as well as ISA support. Arm SHA-512 must check its actual hardware capability; Rust's sha3 compiler bundle is not proof that every CPU exposing another SHA3 facility also has FEAT_SHA512.
  • Modern facade features must never admit legacy crates. Legacy SHA-1 and MD5 retain separate explicit package selection and collision-weakness warnings.
  • Operational APIs must compile and execute from normal extracted packages, without repository evidence cfgs. The new raw static API meets this package gate; the original high-level candidate APIs still do not.
  • Hardened ownership is sealed, affine and mandatory, with equivalent cleanup for lanes, temporaries, metadata, outputs and every lifecycle exit. Ordinary acceleration does not approve hardened execution. Unsupported hardened routes stay portable under Prefer or reject under Require; never degrade ownership.
  • RV64 Zknh currently has QEMU-only instruction evidence. Operational RISC-V acceleration is postponed until qualifying native hardware is available; portable support and existing candidate tests remain unchanged. No new experimental ordinary route, hardened RV64 or RVV claim is scheduled by the remaining pre-HMAC milestones. QEMU alone does not end this deferral.

The inventory names the current exact symbols, compiler features, existing leaf features and activation versions. Family dates do not promise every kernel: each route must also satisfy its kernel's activation and profile disposition, including RV64's hardware-dependent deferral. SHA-2 ordinary/hardened activation is v0.24.33/.34; SHA-3/SHAKE, cSHAKE and hardened Keccak are .35/.36/.37; KMAC, TupleHash and ParallelHash integration is .38/.39/.40. Legacy SHA-1 uses .41/.42 and MD5 .43/.44. Missing multi-message kernels, x86 SHA-512, package reachability and final consumer/native closure span .45–.55. Named SHA-2 and all 510 general t values, arbitrary-bit inputs, XOF outputs and all four fixed/XOF derived-function identities keep their existing complete API domains.

Executable specification, not a crypto API

assurance/acceleration-contract is a dependency-free no_std, unpublished model. Its public ContractSession::begin(Request) only permits portable operation or reported fallback; Require rejects every candidate. Private unit-test predicates exercise future truth tables but are not downstream authority. Public enums are diagnostics and requests, never permits. finish(self) consumes the model. There is no algorithm execution, output buffer, runtime detector or new facade API in this fixture. Final production API spelling remains an activation task.

Run from the repository root:

python3 scripts/cpu/check-acceleration-availability.py
python3 scripts/cpu/test-acceleration-availability.py
cargo test --locked --offline --manifest-path assurance/acceleration-contract/Cargo.toml

The checker binds the reviewed contract and complete inventoried owner sources. Mutation tests reject claim promotion and source drift. Compiled model mutants must compile and then fail behavior tests (compiler failure is not a pass). The repository driver runs dedicated all-target Clippy with warnings denied for this standalone workspace. Structural regressions reject removal or weakening of that command; five rustc-valid mutants must each fail their specific declared Clippy security lint. Root-workspace Clippy alone does not cover this fixture. Doctests reject forged/private ownership and finalized reuse. These tests are not cryptographic correctness, timing, native qualification or FIPS evidence. Activation requires new implementation and evidence; historical captures are never rewritten to claim this model executed an instruction.