I run a Bitcoin wallet that uses browser side Javascript to encrypt and decrypt Bitcoin keys.

I want to make the javascript available for scrutiny on Github, and then load the javascript from the github repository.

My problem is I need to check the integrity of the loaded Javascript to ensure at hasn't been tampered with at Github.

How can I best do this ? Would it be something like.

1. Load remote Javascript with an ajax call.
2. MD5 hash and pare.
3. If in good shape execute it.

I run a Bitcoin wallet that uses browser side Javascript to encrypt and decrypt Bitcoin keys.

I want to make the javascript available for scrutiny on Github, and then load the javascript from the github repository.

My problem is I need to check the integrity of the loaded Javascript to ensure at hasn't been tampered with at Github.

How can I best do this ? Would it be something like.

1. Load remote Javascript with an ajax call.
2. MD5 hash and pare.
3. If in good shape execute it.

• javascript

• 2 Couldn't the client mess with the checksum puting function itself? – Anirudh Ramanathan Commented Mar 18, 2013 at 15:01
• Maybe store your code on another server. A CDN that only you can access. That way you can be sure it's fine. – gen_Eric Commented Mar 18, 2013 at 15:01
• How crucial is this at the point of checking if client-side? I'm pretty sure you know client-side is not safe in practically any way. The integrity check really must be done by a server-side script and then feed it back to the JavaScript, otherwise you will face immense security problematics. – user1467267 Commented Mar 18, 2013 at 15:02
• Anything that runs in a browser can be tampered with. Either directly or scripts loaded with an extension or add on. – datasage Commented Mar 18, 2013 at 15:02
• 4 I'm pretty sure that using github as a CDN is explicitly discouraged. – Pointy Commented Mar 18, 2013 at 15:02

1 Answer 1

There is (or soon WILL be) an elegant way to achieve this now (2 years after the question was asked).

http://www.w3/TR/SRI/

You can now specify the "integrity" parameter inside the script tag:

<script src="https://github./<path>/yourscript.js"
        integrity="sha256-SDf......">

This won't work for the script loaded via an AJAX requests. But you can potentially reference scripts as script tags pointing at the CDN (ideally not at github directly)