Add Ed25519 sign-verify example

[guest271314]

See mdn/content#30886

[bsmth]

Thanks for the submission. This doesn't work for me using Chrome Canary / Beta:

• ❌ Version 123.0.6264.0 (Official Build) canary (arm64)
• ❌ Version 122.0.6261.6 (Official Build) beta (arm64)

I don't see any preferences / flags to enable.

The following works in node:

async function generateAndSignKey() {
  const algorithm = { name: "Ed25519" };
  const encoder = new TextEncoder();
  const cryptoKey = await crypto.subtle.generateKey(
    algorithm,
    true,
    ["sign", "verify"]
  );

  console.log(
    await crypto.subtle.sign(
      algorithm,
      cryptoKey.privateKey,
      new Uint8Array([255])
    )
  );
}

generateAndSignKey();

With an exp warning:

(node:27247) ExperimentalWarning: The Ed25519 Web Crypto API algorithm is an experimental feature and might change at any time
(Use `node --trace-warnings ...` to show where the warning was created)
ArrayBuffer {
  [Uint8Contents]: <bd 47 7d 05 81 ff e2 98 02 6e 16 4e cd 49 9a 1c 9f 5b 6d 5c 49 a0 f6 98 eb 29 3c 0c 4d 3e 28 43 b7 9a dd c2 df ef 4b ca 80 de 2e 04 59 02 7e 08 95 c5 c8 5c 3d d9 4c aa 65 20 0d 00 2e 1c 2e 0b>,
  byteLength: 64
}
...
node --version
v20.11.0

[guest271314]

Launch Chrome or Chromium with --enable-experimental-web-platform-features command-line switch (updated with link in index.html).

E.g., for testing

~/chrome-linux/chrome --user-data-dir=$HOME/test --password-store=basic --enable-experimental-web-platform-features file:///home/user/sign-verify/index.html

[bsmth]

Confirmed this is working, also possible via chrome://flags/#enable-experimental-web-platform-features as an alternative to command-line arg. See;

• https://chromestatus.com/feature/4913922408710144
• https://wpt.live/WebCryptoAPI/generateKey/successes_Ed25519.https.any.html

[bsmth]

Closed by mistake, please ignore

[bsmth]

Leaving a +1 on this, thank you!

[bsmth]

Thanks a lot for your review @twiss, I've incorporated your feedback and I'm happy to merge in the current state unless you have any objections!