Jint

Crypto and performance ​

Web Crypto ​

WebApiFeatures.Crypto provides crypto.getRandomValues, crypto.randomUUID, and crypto.subtle. The subtle API supports its twelve standard operations over SHA digests, HMAC, AES-CTR/CBC/GCM/KW, RSA signatures and OAEP, ECDSA/ECDH on the NIST curves, HKDF, and PBKDF2.

csharp
var engine = new Engine(options =>
    options.UseWebApis(WebApiFeatures.Crypto | WebApiFeatures.Encoding));

var digest = await engine.EvaluateAsync("""
    crypto.subtle.digest('SHA-256', new TextEncoder().encode('hello'))
    """);

Cryptographic work is synchronous and the returned promises are already settled. Script failures are promise rejections.

The implementation uses .NET cryptography and exposes a few platform limits: AES-GCM requires a 96-bit IV and supported .NET tag sizes; RSA-PSS accepts the hash-sized salt; RSA-OAEP labels must be empty; generated RSA keys use exponent 65537 and are capped at 8192 bits; PBKDF2 is capped at 4,194,304 iterations. These caps bound BCL operations that execution constraints cannot interrupt. Treat key extraction and persistence as host security decisions.

Performance timeline ​

WebApiFeatures.Performance provides performance.now(), timeOrigin, marks, measures, entry queries, and PerformanceObserver.

javascript
performance.mark('start');
for (let i = 0; i < 1000; i++) Math.sqrt(i);
const measure = performance.measure('work', 'start');
console.log(measure.duration);

The timeline retains at most 10,000 entries; clear marks and measures when they are no longer needed. PerformanceObserver callbacks are queued microtasks and run only while the engine is pumped.

Timers and performance share Options.WebApi.Timers.TimeProvider, allowing deterministic tests without a background timer. Jint does not reduce timer precision: if untrusted code should not receive a high-resolution clock, do not enable this feature or provide an appropriately coarse TimeProvider.