runtime:hashing

Digests, checksums, MACs and password hashing. crypto.subtle is the WebCrypto standard; this is the rest — the algorithms it has no name for, hashing that runs incrementally, encoded output, and passwords.

Capability: none

Hashing reads nothing and reaches nothing, so every function here works under nothing granted. The exception is password.hash(), which draws a random salt and so needs Entropy; password.verify() needs nothing. Status: Available.

Import

JavaScript

import { hash, Hasher, hashStream, hmac, timingSafeEqual, password } from "runtime:hashing";

// Or the default aggregate:
import hashing from "runtime:hashing";

Exports

Export	Type	Description
`hash`	`function`	`hash(algorithm, data, encoding?)` — the digest, in one call.
`Hasher`	`class`	`new Hasher(algorithm)` — a hash across many chunks.
`hashStream`	`async function`	`hashStream(algorithm, stream, encoding?)`.
`hmac`	`function`	`hmac(algorithm, key, data, encoding?)` — RFC 2104, synchronous.
`timingSafeEqual`	`function`	`timingSafeEqual(a, b)` — constant-time comparison.
`password`	`object`	`hash()`, `verify()`, `needsRehash()`.

data, key and the comparands are a string (hashed as UTF-8), an ArrayBuffer, or a view. encoding is "hex", "base64" or "base64url" for a string; omit it for a Uint8Array.

Algorithms

Algorithm	Output	Notes
`sha1` `sha256` `sha384` `sha512`	20 / 32 / 48 / 64 B	Also in `crypto.subtle`.
`sha3-224` `sha3-256` `sha3-384` `sha3-512`	28 / 32 / 48 / 64 B
`blake3`	32 B	Fast. The usual choice for large content.
`md5`	16 B	Interop only — S3 ETags, CRAM-MD5.
`ripemd160`	20 B
`xxhash64` `xxhash3`	8 B	Not cryptographic. Cache keys, ETags, sharding.
`crc32` `crc32c`	4 B	Not cryptographic. Checksums, framing.

Names are case-insensitive, and WebCrypto's spellings work: "SHA-256" and "sha256" are the same algorithm. hmac refuses the two non-cryptographic rows.

JavaScript

hash("sha256", "hello", "hex");   // "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"
hash("blake3", "hello", "base64url");
hash("xxhash3", buffer);          // Uint8Array

Hasher

JavaScript

const h = new Hasher("sha256");
for await (const chunk of file.stream()) h.update(chunk);
h.digest("hex");

Member	Type	Description
`algorithm`	`string`	Read-only.
`update(data)`	`this`	Chains.
`digest(encoding?)`	`Uint8Array \| string`	Ends the hasher.

digest() releases the host state; calling either method again throws.

JavaScript

// The same, in one line.
await hashStream("sha256", request.body, "hex");

timingSafeEqual

For anything an attacker can submit repeatedly. === on hex strings leaks how much of the prefix was right, one request at a time.

JavaScript

const expected = hmac("sha256", secret, body, "hex");
if (!timingSafeEqual(request.headers.get("x-signature"), expected)) {
  return new Response("bad signature", { status: 401 });
}

Lengths are compared first, in ordinary time — a digest's length is fixed by its algorithm and public already.

password

Argon2id by default; bcrypt and scrypt for hashes that already exist.

JavaScript

const stored = await password.hash(input);       // "$argon2id$v=19$m=19456,t=2,p=1$…"
await password.verify(input, stored);

Option	Applies to	Default
`algorithm`	all	`"argon2id"` · `"argon2i"` `"argon2d"` `"bcrypt"` `"scrypt"`
`memoryCost`	argon2	`19456` KiB
`timeCost`	argon2	`2` passes
`parallelism`	argon2, scrypt	`1`
`cost`	bcrypt, scrypt	`12` rounds log₂ / `17` N log₂
`blockSize`	scrypt	`8`
`salt`	all	16 random bytes

Defaults follow the OWASP Password Storage Cheat Sheet.

Method	Type	Capability
`hash(input, options?)`	`Promise<string>`	Entropy
`verify(input, stored)`	`Promise<boolean>`	—
`needsRehash(stored, options?)`	`boolean`	—

The stored string carries the algorithm, parameters and salt, and verification reads them from it — so raising the cost never invalidates existing hashes.

JavaScript

if (await password.verify(input, user.hash)) {
  if (password.needsRehash(user.hash)) user.hash = await password.hash(input);
}

Two things to know

These are slow on the thread that calls them — that is the mechanism. Put a queue in front of a login endpoint. And bcrypt refuses a password past 71 bytes rather than truncating it; verification still truncates, since a stored hash may have been written by an implementation that did.