The SubtleCrypto Digest Architecture
The `window.crypto.subtle.digest('SHA-256', buffer)` method converts arbitrary ArrayBuffers into 32-byte cryptographic hashes in microseconds.
Transforming the resulting ArrayBuffer into a readable hexadecimal string requires mapping each byte with `.toString(16).padStart(2, '0')`.
HMAC-SHA256 Key Import and Signing
Calculating a Keyed-Hash Message Authentication Code (HMAC) requires first importing the shared secret key via `subtle.importKey('raw', keyBuffer, { name: 'HMAC', hash: 'SHA-256' }, false, ['sign'])`.
Once imported, calling `subtle.sign('HMAC', key, dataBuffer)` generates the tamper-proof signature.
Step-by-Step Tutorial
Encode Text to Uint8Array
Use const msgUint8 = new TextEncoder().encode('my secret payload');
Execute Cryptographic Digest
const hashBuffer = await crypto.subtle.digest('SHA-256', msgUint8);
Format Hexadecimal Output
Convert the hash buffer to a standard 64-character hex string for comparison.
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Frequently Asked Questions
Is Web Crypto API available in Web Workers?
Yes. self.crypto.subtle is fully available inside Dedicated Web Workers and Service Workers for background hashing.
Can Web Crypto hash a 1GB file without freezing the UI?
Yes! By reading the file in chunks using FileReader or File.stream(), SubtleCrypto hashes large files smoothly in background threads.