self-decrypting-html-page

Generate a standalone HTML page that decrypts an encrypted message. Used by html-vault.

The idea is to have a tool that encrypts any message/secret and generates something that can decrypt itself. I see two advantages of the HTML-based solution over others:

low entry-barrier: Everyone has a web browser. Everyone with a reasonably modern browser will be able to use the tool, without installing anything. It is also more platform-independent than other solutions.
self-contained: The generated page has all the logic built-in that it needs to decrypt the encrypted message. It can be stored as a standalone file.

With self-decrypting-html-page, you can use this functionality anywhere. Consider the examples below.

Usage from the command line

There are three ways to install this tool:

standalone binaries from the releases page
installing globally using npm: npm install -g self-decrypting-html-page
temporarily installing it into a temp directory and running it, using npx: npx self-decrypting-html-page

# basic usage
echo 'my secret message' | npx self-decrypting-html-page >encrypted-message.html
# This is your key:
# 964d87e28a7f468afe33c255e689d2baa5d67dabc43d6262971a5efd18917929

# write decryption key to file
echo 'my secret message' | npx self-decrypting-html-page >encrypted-message.html 2>key.txt
cat key.txt
# 964d87e28a7f468afe33c255e689d2baa5d67dabc43d6262971a5efd18917929

Usage with JS

npm i self-decrypting-html-page

const encryption = require('sodium-encryption')
const generateHTML = require('self-decrypting-html-page')

const msg = Buffer.from('super secret message')
const key = encryption.key()
console.log('key:', key.toString('hex'))

const nonce = encryption.nonce()
const encrypted = encryption.encrypt(msg, nonce, key)
const html = generateHTML(nonce, encrypted)
// write this HTML to a file, open in the browser

Usage with custom HTML template

Write the template for self-decrypting HTML page. Check decrypt.html for the necessary elements.

Generating a custom self-decrypting HTML page from the command line:

echo 'my secret message' | npx self-decrypting-html-page --html path/to/template.html >encrypted-message.html

Generating a it using JS:

const {readFileSync} = require('fs')
const {join} = require('path')
const generateHTML = require('self-decrypting-html-page/custom-html')

const template = readFileSync(join(__dirname, 'template.html'))
const html = generateHTML(nonce, encrypted, template)

How it works

lib/decrypt.js contains the logic to decrypt the message, using the nonce and the password entered by the user.
lib/decrypt.js gets bundled with all its dependencies and stored in decrypt.js, using Browserify.
Then, using brfs, the generated bundle will be inserted into another JS file generate.js. The version of self-decrypting-html-page published to npm already contains it.
When you call generateHTML(nonce, encrypted) or run it from the command line, it will replace placeholders in the HTML (that already contains the code to decrypt) and give the final string back to you.

Contributing