ALTCHA JS Library

ALTCHA JS Library is a lightweight, zero-dependency library designed for creating and verifying ALTCHA challenges specifically tailored for Node.js, Bun, and Deno environments.

Compatibility

This library utilizes Web Crypto and is intended for server-side use.

• Node.js 16+
• Bun 1+
• Deno 1+

Usage

import { createChallenge, verifySolution } from 'altcha-lib';

const hmacKey = 'secret hmac key';

// Create a new challenge and send it to the client:
const challenge = await createChallenge({
  hmacKey,
});

// When submitted, verify the payload:
const ok = await verifySolution(payload, hmacKey);

API

createChallenge(options)

Creates a new challenge for ALTCHA.

Parameters:

• options: ChallengeOptions:
  • algorithm?: string: Algorithm to use (SHA-1, SHA-256, SHA-512, default: SHA-256).
  • hmacKey: string (required): Signature HMAC key.
  • maxNumber?: number Optional maximum number for the random number generator (defaults to 1,000,000).
  • number?: number: Optional number to use. If not provided, a random number will be generated.
  • salt?: string: Optional salt string. If not provided, a random salt will be generated.
  • saltLength?: number Optional maximum lenght of the random salt (in bytes, defaults to 12).

verifySolution(payload, hmacKey)

Verifies an ALTCHA solution. The payload can be a Base64-encoded JSON payload (as submitted by the widget) or an object.

Parameters:

• payload: string | Payload
• hmacKey: string

License

MIT