Secure online browsing - check TSL fingerprint to avoid MiTM - worked example using Stalking Directory

zambezi

Well-Known Member
Browsing online was hideously insecure when we connected to websites using unencrypted http:// url links.

With the advent of SSL [now TSL], the link your browser makes with your bank's website, or the Stalking Directory, etc is (1) validated by [CA derived] certificates bundled in your browser and (2) secured with session encryption. I.e. https://

The number and quality of certificate authorities has varied down the years, and there have been some blatant counterfeits leading to man-in-the-middle attacks where a user's web browsing is viewed by the issuer of a fake certificate.

Certificates can be faked. The associated digital fingerprints not. So it is possible to verify if your browser is connected to the endpoint you expect or if your data is washing through a third party.

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Scroll down to the fingerprint section:

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Now open web server encryption test (SSL / HTTPS Check) · SSL-Tools and insert the url you are verifying. In our example: thestalkingdirectory.co.uk

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....last step is to verify a match between the fingerprint declared to your browser by the connected endpoint also matches the CA-derived official fingerprint for that domain. I will distil into smaller slides in next post...
 
(1) Discover fingerprint of certificate by which your browser has validated connection to target website

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(2) Independently discover what the officially registered fingerprint is associated with the URL to which you have connected in the browser above [caveat at bottom]

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One caveat to this process: larger entities like Google can have multiple certificates for same url. In the third pane of step (1) above you will see that there are a swathe of Subject Alt Names. In practice, I have usually found that recursive checking of these eventually finds a match.


This process is not for everyone. It is not for every online activity. But MiTM is set to be a bigger problem going forward. Bookmark this page. You may be coming back to it...
 
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