this post was submitted on 21 May 2024
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All TLS/HTTPS clients have a set of Certificate Authority keys which they trust. Your client will only accept a public key which is signed by a trusted CA's key. A proper CA will not sign a key for a domain when it has not verified that the entity that wants it's key signed actually controls the domain.
Most browsers trust many certificate authorities from all over the world.
Any of them could...
...and yes, it has happened already.
HTTPS as most of us use it today is useful, but far from foolproof. This is why various additional measures, like certificate pinning, private CAs, and consensus validation are sometimes used.
This is slightly off-topic but I was thinking about it and all of thoes isues can be solved by utilizing blockchain. Imagine a world where instead of CAs, decentralized domain (unstoppable domains, ENS etc.) owners publish their pub keys to the blockchain, the client can than query multiple nodes or store the chainstate locally. When establishing a connection client sends a secret handshake message + clients' pub key encrypted with domains' pub key. To complete the handshake server responds with the same secret message encrypted with clients' pub key.
It seems to me like a MITM hacker can just redirect all requests to a Blockchain node towards their malicious node.
Ownership of the domain is verifiable on the blockchain, if the same wallet that owns the domain (nft) also publishes the pub key (owns the pub key nft or key data is embedded in the domain name nft) you can verify that the key is valid.
IMO blockchain is more trustworthy than any single CA because you aren't trusting a single entity, but a decentralized network of nodes. Assuming that most nodes are honest you can query 100 independent nodes for the same data, if 99 say the same thing you can be fairly confident that the data is valid. You can also run your own node and not have to trust anyone.
To protect against MITM of your connection redirecting all traffic to their malicious node, some well known and trusted nodes would be hardcoded in the browser/OS software along with their public signing key to verify the signed data they send you, and genesis block data in case you want to run a node yourself. Signing keys of nodes would also be published to the blockchain. Think a unified, immutable, cryptographically verifiable, distributed database of public key - domain name pairs, which is what blockchain basically is. Encrypting the connection is a good idea too, extra privacy is always welcome.
The biggest advantage here is that every single pub key (certificate) is stored by every single node (CA), so if one node goes rogue or is compromised and starts serving false data, it will be immediately discovered by the client by comparing it's data to the data from other nodes, and can be immediately and verifiably reported to the network, even in the case of a targeted attack, because all data recived from the nodes is signed.
No solution is perfect and this one is not an exception, if your hardware or your os/browser is compromised there is nothing short of manually checking certificate data or using an external device to verify it, that can be done, but that's true for most IT systems, including the current TLS certification and authority based system.
Blockchain is a well tested technology that has proven itself to work by being a core part of a trillion dollar industry and was specifically designed to eliminate the need for trusting a 3rd party. It seems like a natural solution to the biggest problem with CAs - trusting a 3rd party. It's honestly sad that so many people dismiss it or are downright against it coz "crypto", even when no crypto currency is invloved. I guess they spent so much time hating it they can't even admit it might be useful to them after all.
Thanks for asking for a follow-up instead of just downvoting.