StatiCrypt

Based on the crypto-js library, StatiCrypt uses AES-256 to encrypt your string with your passphrase in your browser (client side).

Download your encrypted string in a HTML page with a password prompt you can upload anywhere (see example).

You can encrypt a file online at https://robinmoisson.github.io/staticrypt.

HOW IT WORKS

StatiCrypt generates a static, password protected page that can be decrypted in-browser: just send or upload the generated page to a place serving static content (github pages, for example) and you're done: the javascript will prompt users for password, decrypt the page and load your HTML.

It basically encrypts your page and puts everything with a user-friendly way to use a password in the new file.

AES-256 is state of the art but brute-force/dictionary attacks would be trivial to do at a really fast pace: use a long, unusual passphrase.

Disclaimer: The concept is simple and should work ok but I am not a cryptographer, if you have sensitive banking or crypto data you might want to use something else. :)

You can report thoughts and issues to the GitHub project but be warned I might be extremely slow to respond (though the community might help). If a serious security issue is reported I'll try to fix it quickly.

CLI

Staticrypt is available through npm as a CLI, install with npm install -g staticrypt (with or without the -g flag) and use as follow:

Usage: staticrypt <filename> <passphrase> [options]

Options:
  --help                    Show help                                   [boolean]
  --version                 Show version number                         [boolean]
  -e, --embed               Whether or not to embed crypto-js in the page (or use 
                            an external CDN)
                                                       [boolean] [default: true]
  -o, --output              File name / path for generated encrypted file
                                                        [string] [default: null]
  -t, --title               Title for output HTML page
                                            [string] [default: "Protected Page"]
  -i, --instructions        Special instructions to display to the user.
                                                        [string] [default: null]
  -f, --file-template       Path to custom HTML template with password prompt.
                          [string] [default: "[...]/cli/password_template.html"]
  -r, --remember            Show a "Remember me" checkbox that will save the
                            (salted + hashed) passphrase in localStorage when
                            entered by the user.
                            You can set the expiration in days as value (no
                            value means "0", no expiration).        [number]
  --remember-label          Label to use for the "Remember me" checkbox.
                            Default: "Remember me".
                                           [string] [default: "Remember me"]
  --passphrase-placeholder  Placeholder to use for the passphrase input.
                            Default: "Passphrase".
                                            [string] [default: "Passphrase"]
  --decrypt-button          Label to use for the decrypt button. Default:
                            "DECRYPT".         [string] [default: "DECRYPT"]

Example usages:

• staticrypt test.html mySecretPassphrase -> creates a test_encrypted.html file
• find . -type f -name "*.html" -exec staticrypt {} mypassword \; -> create encrypted files for all HTML files in your directory

You can use a custom template for the password prompt - just copy cli/password_template.html and modify it to suit your presentation style and point to your template file with the -f flag. Be careful to not break the encrypting javascript part, the variables replaced by staticrypt are between curly brackets: {instructions}.

--remember

This will add a "Remember me" checkbox. If checked, when the user enters their passphrase its salted hashed value will be stored in localStorage. In case this value becomes compromised an attacker can decrypt the page, but this should hopefully protect against password reuse attack (of course please use a unique passphrase nonetheless).

This allows encrypting multiple page on a single domain with the same password: if you check "Remember me", you'll have to enter you password once then all the pages on that domain will automatically decrypt their content.

If no value is provided the stored passphrase doesn't expire, you can also give it a value in days for how long should the store value be kept. If the user reconnects to the page after the expiration date the store value will be cleared.

You can clear the values in localStorage (effectively "login out") at any time by appending staticrypt_logout to the URL query paramets (mysite.com?staticrypt_logout).

--embed and crypto-js

If you do not embed crypto-js and serve it from a CDN, some adblockers see the crypto-js.min.js, think that's a crypto miner and block it.

Contribution

Thank you: @AaronCoplan for bringing the CLI to life, @epicfaace & @thomasmarr for sparking the caching of the passphrase in localStorage (allowing the "Remember me" checkbox)

Opening PRs: You're free to open PRs if you're ok with having no response for a (possibly very) long time and me possibly ending up getting inspiration from your proposal but merging something different myself (I'll try to credit you though). Apologies in advance for the delay, and thank you!

If you find a serious security bug please open an issue, I'll try to fix it relatively quickly.

Alternatives

https://github.com/MaxLaumeister/PageCrypt is a similar project (I think it predates staticrypt).

https://github.com/tarpdalton/staticrypt/tree/webcrypto is a fork that uses the WebCrypto browser api to encrypt and decrypt the page, which removes the need for crypto-js. There's a PR open which I haven't checked in detail yet. WebCrypto is only available in HTTPS context (which is annoying people) so it won't work if you're on HTTP.