The security-sensitive counterpart to the fast, non-cryptographic Hash.*
library: standard, test-vector-backed hashing for signed saves and message
integrity, kept in its own namespace so nobody reaches for the wrong tool.
Crypto.sha256(s) SHA-256 -> 64-char lowercase hex
Crypto.hmac_sha256(key, msg) HMAC-SHA256 -> 64-char hex
Crypto.verify_hmac(key, msg, mac) recompute + constant-time compare -> bool
Crypto.hex(s) lowercase hex of a string's bytes
Crypto.ct_equal(a, b) constant-time string equality
The primitives are implemented from scratch in plain integer LLVM IR
(FIPS 180-4 / RFC 2104): no libc crypto, no data-dependent branches in the
compression rounds, so a given input hashes to the same 32 bytes on every
platform and run. Digests are returned as hex strings, not raw bytes, because
a `str` is null-terminated and a raw digest can contain a NUL. MAC checks use
a non-short-circuiting compare so timing does not leak how much of a forged tag
was correct.
Emitted on demand via g_uses_cryptort, mirroring the emit_hash prelude gate.
Scoped to the deterministic, known-answer-testable core; OS-backed
random_bytes (the one piece that can't be validated by test vectors) is left
for a follow-up.
Tested against published SHA-256 vectors (empty/"abc"/fox + 55/56/64-byte
multi-block padding) and HMAC-SHA256 vectors; wired into the self-host suite as
`crypto`. Docs: a new Crypto section with honest "what this protects / does
not" guidance, one page per method, all fences checked and in the inventory.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
