Crypto & encoding

SHA-256, base64 and UUIDs from Web Crypto — answers no model can guess, only compute.

Try it live → — load a model once in the demo, then ask one of the questions below.

What it shows

A hash is the purest test of whether a tool was really called: there is no way to produce b94d27b9… for “hello world” from memory. sha256 uses crypto.subtle.digest, base64 encodes and decodes UTF-8 safely, uuid uses crypto.randomUUID().

The tools file

Web Crypto, in the tab. A hash is the purest test there is: no model can guess one.

// Web Crypto and encoding. The answers cannot be guessed, only computed.

tool('sha256', 'Compute the SHA-256 hash of a text, returned as hex.',
  { text: 'string' },
  async ({ text }) => {
    const buf = await crypto.subtle.digest('SHA-256', new TextEncoder().encode(String(text)));
    return { text, sha256: [...new Uint8Array(buf)].map((b) => b.toString(16).padStart(2, '0')).join('') };
  });

tool('base64', 'Encode text to base64, or decode base64 back to text.',
  { text: 'string', mode: { type: 'string', enum: ['encode', 'decode'] } },
  async ({ text, mode }) => {
    if (mode === 'decode') {
      const bytes = Uint8Array.from(atob(String(text)), (c) => c.charCodeAt(0));
      return { text: new TextDecoder().decode(bytes) };
    }
    const bytes = new TextEncoder().encode(String(text));
    return { base64: btoa(String.fromCharCode(...bytes)) };
  });

tool('uuid', 'Generate a new random UUID.',
  {},
  async () => ({ uuid: crypto.randomUUID() }));

Each tool(name, description, params, handler) is one callable. The file is plain JavaScript, not a module — no imports, no build step, and the demo lets you edit it and apply it live.

Wire it up

import { NexusChat } from 'toolnexus-web';

// loadForTools checks the model can really call a tool before handing it over.
const chat = await NexusChat.loadForTools({ hub: 'onnx-community/Qwen3-0.6B-ONNX' });
await chat.loadTools('./tools.js');   // the file above, saved as tools.js

chat.on('token', (t) => render(t));
chat.on('toolCall', (call, result) => console.log(call.name, result));

const answer = await chat.chat("What is the SHA-256 hash of 'hello world'?");

Questions to try

• What is the SHA-256 hash of ‘hello world’?
• Base64-encode the text ‘toolnexus-web’.
• Generate a new UUID for me.

What to expect

Not measured by the harness yet. Compare the hash in the answer with the one in the tool log — a small model sometimes truncates or retypes long hex strings when it reports them.

Going further

Web Crypto also signs, verifies, encrypts and derives keys — all in the tab, all without a server. Web Crypto needs a secure context (HTTPS or localhost).