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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>
26 lines
1 KiB
Markdown
26 lines
1 KiB
Markdown
---
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id: crypto-sha256
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name: Crypto.sha256
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category: crypto
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kind: namespace-method
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tokens: Crypto.sha256
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sig: Crypto.sha256(s) -> string
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tip: SHA-256 of a string, as 64 hex characters.
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order: 1
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ns: Crypto
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member: sha256
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---
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Computes the SHA-256 digest of the bytes of <code>s</code> and returns it as a 64-character lowercase hex string. This is the standard, FIPS 180-4 algorithm — the same digest every other conforming implementation produces — so it is deterministic across platforms and runs and is backed by published known-answer vectors. Use it to fingerprint content, or as the building block under <a href="crypto-hmac_sha256"><code>Crypto.hmac_sha256</code></a> for signing. On its own SHA-256 is <em>not</em> a message authentication code: anyone can recompute it, so it proves what the data is, not who produced it.
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Parameters:
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- `s` — the string whose bytes are hashed
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```ludic
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program Fingerprint {
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entry {
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let digest = Crypto.sha256("abc")
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print(digest) # ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad
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}
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}
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```
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