@kastov/cryptohapp

A lightweight library for creating Happ crypto deep links. Works on both Node.js (backend) and browser (frontend) environments.

Features

• 🖥️ Backend: Uses native Node.js crypto module (zero dependencies)
• 🌐 Frontend: Uses lightweight jsencrypt library (~30KB)
• 📦 Supports multiple crypto versions (v2, v3, v4)

Installation

Backend (Node.js):

npm i @kastov/cryptohapp

Frontend (Browser):

npm i @kastov/cryptohapp jsencrypt

Usage

Get Full Link (string)

import { createHappCryptoLink } from '@kastov/cryptohapp';

const link = createHappCryptoLink('https://subscription.link.com/s/remnawavetop', 'v4', true);
// Returns: 'happ://crypt4/base64encodeddata...'

if (link) {
  console.log(link); // 'happ://crypt4/base64encodeddata...'
}

Get Separate Parts (object)

import { createHappCryptoLink } from '@kastov/cryptohapp';

const result = createHappCryptoLink('https://subscription.link.com/s/remnawavetop', 'v4');

if (result) {
  console.log(result.deepLink); // 'happ://crypt4/'
  console.log(result.encryptedContent); // 'base64encodeddata...'
}

Error Handling

import { createHappCryptoLink } from '@kastov/cryptohapp';

const result = createHappCryptoLink('https://example.com/subscription', 'v4');

if (result === null) {
  console.error('Encryption failed');
} else {
  console.log('Success:', result.deepLink + result.encryptedContent);
}

React Example

import { useState } from 'react';
import { createHappCryptoLink } from '@kastov/cryptohapp';

function CryptoLinkGenerator() {
  const [link, setLink] = useState('');

  const generateLink = () => {
    const cryptoLink = createHappCryptoLink(
      'https://subscription.link.com/s/remnawavetop',
      'v4',
      true,
    );

    if (cryptoLink) {
      setLink(cryptoLink);
    }
  };

  return (
    <div>
      <button onClick={generateLink}>Generate Crypto Link</button>
      {link && <a href={link}>Open in Happ</a>}
    </div>
  );
}

NestJS Example

import { Injectable } from '@nestjs/common';
import { createHappCryptoLink } from '@kastov/cryptohapp';

@Injectable()
export class HappService {
  generateCryptoLink(subscriptionUrl: string): string | null {
    return createHappCryptoLink(subscriptionUrl, 'v4', true);
  }
}

API Reference

createHappCryptoLink(content, version, asLink?)

Creates an encrypted Happ deep link.

Parameters

Parameter	Type	Default	Description
content	string	—	The content to encrypt (e.g., subscription URL)
version	'v2' | 'v3' | 'v4'	—	Crypto version to use (required)
asLink	boolean	false	When true, returns full link string

Returns

When asLink is true: string | null

const link = createHappCryptoLink(content, 'v4', true);
// Returns: 'happ://crypt4/base64encodeddata...' or null

When asLink is false or omitted: HappCryptoResult | null

interface HappCryptoResult {
  /** Deep link prefix (e.g., 'happ://crypt4/') */
  deepLink: string;
  /** Base64 encoded encrypted content */
  encryptedContent: string;
}

Returns null if encryption fails.

Exported Constants

You can also access the public keys directly:

import { HAPP_CRYPTO_V2, HAPP_CRYPTO_V3, HAPP_CRYPTO_V4 } from '@kastov/cryptohapp';

console.log(HAPP_CRYPTO_V4.publicKey); // RSA public key
console.log(HAPP_CRYPTO_V4.deepLink); // 'happ://crypt4/'

How It Works

The library uses RSA encryption with PKCS1 padding to encrypt your content:

• Backend: Uses Node.js native crypto.publicEncrypt()
• Frontend: Uses jsencrypt library for browser compatibility

Both implementations produce identical encrypted output, ensuring cross-platform compatibility.

Content Size Limits

RSA with PKCS1 padding can encrypt data up to (keySize / 8) - 11 bytes. For a 4096-bit key, this is approximately 501 bytes. If your content exceeds this limit, consider using a URL shortener or compression.

Reference

• Happ Crypto Link Documentation

License

MIT