How can I get the public key of a website like VeriSign and all other websites which use https(secure protocol)?
It depends on the browser you're using, if you let me know I'll update my answer.
Chrome 55 and above You can now find this information in Developer Tools. Options (3 dots) -> More Tools -> Developer tools, or press F12, then click the "Security" tab and you'll get a "Security Overview" with a "View certificate" button. As per another SO post from Chrome 60 you can actually enable the option again if you go to chrome://flags/#show-cert-link
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Chrome 54 and below: If you're using Chrome then click on the green bar to the left of the 'https:' in the address bar, for the VeriSign website the green bar says Symantec Corperation [US]
, this will open a pop up. On the pop up click 'Certificate Information'. This will open another pop up. On this go the 'Details' tab at the top and scroll down to 'Public key' which shows the public key the website is using for it's SSL. In VeriSigns case the public key is a 2048 bit key.
IE: the green bar to click on is to the right of the web address. Clicking this brings a similar pop up where you have to click 'View certificates' which then brings up the same pop up as on Chrome where you go to the Details tab and scroll down to 'Public Key'
This is the pop up that opens after clicking the 'Certificate information' or 'View certificates' links.