Anti-MitM TLSCAPTCHA (PoC) by Anon

This extension uses your CAPTCHA answer to verify TLS certificate that you get from website you're visiting. Warning: you can see it in action only if a website has server-side part of such verification scheme.

3 (2 reviews)

15 Users

You'll need Firefox to use this extension

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About this extension

Every time when you solve CAPTCHA, the CAPTCHA answer can be used as a common secret for a short time. Mainly, It can be used to prevent TLS certificate spoofing.

Since ordinary web pages (and their JavaScript) doesn't have access to TLS certificate data, I was have to make this extension. Actually it does the following:

let clientsideDigest = <Digest of TLS certificate that you get from website you're visiting>;
let yourAnswer = <Your CAPTCHA answer>;
let resultDigest = PBKDF2(clientsideDigest, "SHA-512", yourAnswer);
//Where yourAnswer is PKBDF2 salt.
cookies["TLSCaptcha"] = representAsHexString(resultDigest);

To see it in action, you need to visit a website that have server-side implementation of this scheme.
At the moment of publishing this extension, there is no server-side implementations. If you want to make your own, please look into source code for details.

New additional featue: you can use this addon to establish additional encryption. See source code for details.

Developer comments

At the moment of publishing this extension, there is no server-side implementations. If you want to make your own, please look into source code for details. It's very simple to understand.

WARNING: this extension cannot be ported to Chromium-based browsers due to API limitations.

Rated 3 by 2 reviewers

Release notes for 1.0.3

~ Content script is no more.
~ Works properly with 'insecure context'.
~ Breaking change: only PBKDF2 is supported as verification hash.
+ Experimental feature: encrypted content support.

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