What it is
Certimark is a browser extension that checks the TLS certificate of the page you're on against certificates marked on the Bitmark blockchain using the Linkmark protocol. A shield in the toolbar tells you, at a glance, whether the certificate matches what others have independently recorded — and the popup shows a description of the site or page drawn from the marking database.
How it works
Reads the certificate
It takes the SHA-256 fingerprint of the certificate your browser actually loaded.
Checks the chain
It looks that fingerprint up against certificates marked on the Bitmark blockchain for the domain.
Shows the verdict
A coloured shield summarizes the result, with the page's description and the option to mark it yourself.
Get it
Certimark is built into the Lux browser for Android, and is also available as an extension for desktop Firefox. Onion (Tor) sites are recognized as cryptographically secure by design.
API
The lookup is a simple request: https://certimark.cc/check?domain=<domain>
(optionally &path=<path>), returning the marked certificates, weights,
and description for the domain as JSON.