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<header class="nav"><div class="wrap nav-in"><a class="brand" href="index.html"><span class="logo">L</span> Ludic</a><button class="nav-toggle" aria-label="Toggle menu" aria-expanded="false">☰</button><nav class="nav-links"><a href="index.html">Home</a><a href="api.html">API Reference</a><a class="nav-cta" href="https://git.workshopsoft.io/workshopsoft/ludic">Source ↗</a></nav></div></header>
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<div class="crumbs"><a href="api.html">API Reference</a> <span>›</span> <span class="here">Crypto</span></div>
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<div class="item-head"><span class="kind-badge kind-namespace">namespace</span><h1 id="top">Crypto</h1></div>
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<p class="ns-blurb">Secure, test-vector-backed hashing for the handful of security-sensitive things a game actually does: signing a save or leaderboard payload so casual tampering is detectable, and verifying that a network message or token was not forged by someone who does not hold the key. This is the deliberate counterpart to the fast <a href="ns-Hash"><code>Hash</code></a> library — same idea, opposite trade-off. <code>Hash</code> is fast and reversible and must never guard anything; <code>Crypto</code> is <a href="crypto-sha256"><code>SHA-256</code></a> and <a href="crypto-hmac_sha256"><code>HMAC-SHA256</code></a> implemented to the standard, so the algorithms are the ones with published known-answer tests rather than anything home-grown.
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Digests are returned as lowercase hex strings, not raw bytes — a <code>str</code> is null-terminated and a raw digest can contain a zero byte, so hex is the form you can print, store, and compare directly.
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Alongside hashing, this library exposes the OS cryptographically-secure random generator — <a href="crypto-random_bytes"><code>random_bytes</code></a>, <a href="crypto-random_hex"><code>random_hex</code></a>, and <a href="crypto-random_u32"><code>random_u32</code></a> — for tokens, nonces, and <a href="ns-Uuid"><code>Uuid</code></a> generation, plus <a href="crypto-base64"><code>base64</code></a> for moving bytes through text-only channels. The secure-random helpers are deliberately non-deterministic and must never seed the lockstep simulation RNG (<a href="ns-Random"><code>Random</code></a>).
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What this is not: it is not DRM and it is not unbeatable anti-cheat. A client-side game cannot keep a secret from the machine it runs on — a determined owner can always read the key out of the binary. Use it to make *casual* tampering detectable and to authenticate messages between parties who share a key. To verify a MAC always use <a href="crypto-verify_hmac"><code>Crypto.verify_hmac</code></a> (a constant-time check), never <code>==</code>, which leaks how much of a guessed MAC was correct.</p>
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<div class="ns-methods"><a class="ns-method" href="crypto-sha256.html"><code class="nm-sig">Crypto.sha256(s) -> string</code><span class="nm-tip">SHA-256 of a string, as 64 hex characters.</span></a><a class="ns-method" href="crypto-hmac_sha256.html"><code class="nm-sig">Crypto.hmac_sha256(key, msg) -> string</code><span class="nm-tip">Sign a message with a shared secret key.</span></a><a class="ns-method" href="crypto-verify_hmac.html"><code class="nm-sig">Crypto.verify_hmac(key, msg, mac) -> bool</code><span class="nm-tip">Constant-time check that a MAC matches.</span></a><a class="ns-method" href="crypto-hex.html"><code class="nm-sig">Crypto.hex(s) -> string</code><span class="nm-tip">Lowercase hex of a string's bytes.</span></a><a class="ns-method" href="crypto-ct_equal.html"><code class="nm-sig">Crypto.ct_equal(a, b) -> bool</code><span class="nm-tip">Constant-time string equality for secrets.</span></a><a class="ns-method" href="crypto-random_bytes.html"><code class="nm-sig">Crypto.random_bytes(n) -> string</code><span class="nm-tip">n bytes from the OS CSPRNG, as a 2n-character hex string.</span></a><a class="ns-method" href="crypto-random_hex.html"><code class="nm-sig">Crypto.random_hex(n) -> string</code><span class="nm-tip">Alias for random_bytes — n secure bytes as a 2n-char hex string.</span></a><a class="ns-method" href="crypto-random_u32.html"><code class="nm-sig">Crypto.random_u32() -> int</code><span class="nm-tip">One CSPRNG-drawn 32-bit integer.</span></a><a class="ns-method" href="crypto-base64.html"><code class="nm-sig">Crypto.base64(s) -> string</code><span class="nm-tip">Standard base64 (RFC 4648) of a string's bytes.</span></a></div>
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