Posted by hkc 16 hours ago
These would look like nice random values (unlike the ones that were recently compromised), but they would be trivial to generate by anyone who knows the initial inputs (PRNG algorithm, seed, maybe starting byte position, etc.).
Here’s what I understand, every website sends some data encrypted by some key issued by CA and then the browser decrypts it first and then decrypts something in that message, to verify that Google.com, is google.com. I still don’t get why CA’s even exist, not sure what they are solving and how they’re doing it.
The first time you connect to google.com in your browser and get the google.com certificate, your web browser has to decide whether or not to trust that cert. It would be very complicated if every website on the internet had to prove its identity via some sort of out of band process, so web browsers, operating systems, etc all ship with a collection of trusted, institutionally-important certificates which are allowed to vouch for other certificates that aren't yet known to the browser, OS, etc.
Your browser (or whatever HTTPS client) basically says "I've never seen this certificate before, but Lets Encrypt (or Digicert or whoever) says they trust it and we trust Lets Encrypt, so we can treat it as trusted". You as a user are trusting that whatever verification/validation process the CA does is at least good enough to ensure that the owner of the domain is the entity giving you a certificate for that domain.
This is obviously not a perfect system. These CAs can be compromised and break the trust, and they have various levels of validation of the people and companies who come to them and ask to be included in their vouching network, etc. But its a compromise to make sure that users can connect to a wide variety of internet sites, using encryption, without needing to somehow decide whether they themselves trust the certificate provided by the website.
The most important thing to remember is that in most cases the CA is not vouching for the quality or integrity of the website - they are just vouching for whether the person/group who controls the domain/server is also the person/group providing the certificate for encrypted communication with the website. Its a protection against MITM attacks and snooping, not a protection against phishing or anything else that might happen once the connection is established.
The way it’s setup can any CA verify any website, so the weakest link of your CA basically allows an attacker to mimic any website you connect to?
This is the compromise. In exchange for having the ability to easily establish an encrypted connection to pretty much any public web service, the tradeoff is that the entire public internet's encryption is only as good as the operations of the weakest of the big public certificate authorities.
Why are browsers trusting CAs which issued zero certificates since their creation 1 year ago?