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Web Crypto

Background

The Web Crypto API provides a set of low-level functions for common cryptographic tasks. The Workers Runtime implements the full surface of this API, but with some differences in the supported algorithms compared to those implemented in most browsers.

Performing cryptographic operations using the Web Crypto API is significantly faster than performing them purely in JavaScript. If you want to perform CPU-intensive cryptographic operations, you should consider using the Web Crypto API.

The Web Crypto API is implemented through the SubtleCrypto interface, accessible via the global crypto.subtle binding. A simple example of calculating a digest (also known as a hash) is:

const myText = new TextEncoder().encode("Hello world!")
const myDigest = await crypto.subtle.digest(
{
name: "SHA-256",
},
myText, // The data you want to hash as an ArrayBuffer
)
console.log(new Uint8Array(myDigest))

Some common uses include:

Methods

  • crypto.getRandomValues(bufferArrayBuffer)ArrayBuffer
    • Fills the passed ArrayBuffer with cryptographically sound random values.
  • crypto.randomUUID()string

SubtleCrypto Methods

These methods are all accessed via crypto.subtle, which is also documented in detail on MDN.

Supported algorithms

Workers implements all operation of the WebCrypto standard, as shown in the following table. We are happy to add support for more algorithms — let us know about your use case.

A checkmark (✓) indicates that this feature is believed to be fully supported according to the spec. [//]: # An x (✘) indicates that this feature is part of the specification but not implemented. [//]: # If a feature only implements the operation partially, details are listed.

Algorithmsign()
verify()
encrypt()
decrypt()
digest()deriveBits()
deriveKey()
generateKey()wrapKey()
unwrapKey()
exportKey()importKey()
RSASSA PKCS1 v1.5
RSA PSS
RSA OAEP
ECDSA
ECDH
NODE ED255191
AES CTR
AES CBC
AES GCM
AES KW
HMAC
SHA 1
SHA 256
SHA 384
SHA 512
MD52
HKDF
PBKDF2

Footnotes:

  1. Non-standard EdDSA is supported for the Ed25519 curve. Since this algorithm is non-standard, a few things to keep in mind while using it:
  • Use NODE-ED25519 as the algorithm and namedCurve parameters.
  • Unlike NodeJS, we will not support "raw" import of private keys.
  • Since this algorithm is non-standard, the implementation may change over time. While we cannot guarantee it at this time, we will strive to maintain backward compatabilityand compatability with NodeJS's behavior. Any notable compatability notes will be communicated in release notes and via this developer document.
  1. MD5 is not part of the WebCrypto standard, but is supported in Cloudflare Workers for interacting with legacy systems that require MD5. MD5 is considered a weak algorithm. Do not rely upon MD5 for security.

See also