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.
I urge everybody to read up on CAA records in DNS and add them to your domains. They basically say what CA the certs for that domain are supposed to come from. Even if another CA issues valid certs for the domain they would be rejected if they don't match the CAA în DNS. It takes 5 minutes.
You can specify the valid CA in the form of its representative domain, for example to allow Let's Encrypt you'd add
0 issue "letsencrypt.org". If you want to allow multiple CA you add multiple CAA records. They enter into effect if at least one CAA record is present. You can also restrict the challenge type, for example0 issue "letsencrypt.org;validationmethods=dns-01".Please note that this is worth adding a CAA record even if you don't use your domain for HTTP and you don't issue any certs for it, because a rogue CA can do it for you. You can add a blank CAA record (
0 issue ";") which basically forbids any CA.(And yes, this also applies to email. It's worth adding restrictive records even if you don't use your domain for email.)
They mean CAA records:
https://developers.cloudflare.com/ssl/edge-certificates/caa-records/
Right, I'll fix it.
Thats why we now have certificate transparency reports and CA-records.
Sure not perfect, but at least with a compliant CA it wont just happen in the dark.
At some point you have to trust someone.
It is indeed true that some CAs have seriously misbehaved; however, browser builders are rather strict on the presence of the CAs they trust. Misbehaving or even simple errors are reasons for getting kicked out, after which certificates signed by those CAs are now no longer valid.
The certs are still valid.
They are just not implicitly trusted
You are technically correct, best kind of correct
That can be helpful if a transgression is noticed, and it's not orchestrated by a higher authority (e.g. government), and the damage isn't already done.
Of course, browser builders are vulnerable to influence, attack, accidents, questionable judgment, and blind spots just as certificate authorities are.
I agree, it’s far from perfect.
I'm somewhat skeptical. What if LetsEncrypt decided to misbehave tomorrow? Would the browsers have the guts to shut it down and break all sites using it?
Yes, they will. We’ve seen it before in mostly less serious cases: Diginotar, Türktrust, Symantec, etc. As brittle as the CA system can be, when there is real enough trouble, CAs do get revoked.
Not the browser companies. The parent CA would revoke Let's Encrypt's certs and publish that revocation in the certificate revocation list. When the browser (software, running on your system) downloads the new CRL, they will automatically stop trusting LE.
Many years ago I manually removed all CAs from my trust store and only added those I needed. Turned out that from roughly 160 trusted root CAs I needed about 10 to 12. I stopped because it often was very difficult to figure out which CA signed the cert for an app that was failing. The final nail in the coffin was when I was late for a business meeting and the only way to get a parking space close enough to my destination was by paying with an app I'd never used before and finding the right root CA under pressure was too much. I really wish we had more and easier control over who we trust.
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.
How are you ensuring the public key retrieved from the blockchain is legitimate?
You’re just removing the semi trustworthy CA and replacing it with the less trustworthy blockchain. Unless you’re proposing encrypting the blockchain connection, maybe they could use TLS?
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.
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.