Thread

1. bzmrgonz · 1789618128 · focus · HN ↗

   It baffles that people think it's a bad thing to disclose a public key. That's their purpose actually. Sure we now have the post quantum computer threat, and some state actors are harvesting keys, but quantum computer is going to disrupt so much, that Id verification won't even matter really.

   1. morsch · 1789623646 · focus · HN ↗

      Think about it, the key analogy is just terrible. In the origin domain, losing a key is always bad, and making a key available to all is a non sequitur.

      It's not like non-technical people understand asymmetric cryptography. Or even technical people, for that matter.

      Maybe we should refer to the public key as an address, and the private key is just a password again. You can send stuff, securely, to an address. And you can verify the sender when you have their address (ie check the signature).

      1. fc417fc802 · 1789624845 · focus · HN ↗

         The key analogy is perfect for the private key and for symmetric keys. Publishing those is always bad and means you need to rekey immediately just like losing a traditional physical key to a secure building would.

         The public counterpart is tricky to name but I think attaching "public" to it makes the intended usage plenty clear. There isn't really a physical counterpart unless you consider maybe those machines that check for counterfeit cash but even that's not a great fit because the pubkey is simultaneously analogous to a lock box.

         1. tialaramex · 1789636560 · focus · HN ↗

            Not quite. The analogy works for secret keys (what you're calling "symmetric keys") but a private key is unlike real world key analogies because as you'll quickly discover if you deploy real world keys in a high security environment people can examine the lock to figure out the correct key. The whole point of private keys is that this cannot work in a public key system. That step does not exist.

            It is true that publishing your private key is bad but you'd hope the name makes that pretty clear. Despite the way I remember (U2's "The Fly" lyrics, "A secret is something that you tell one other person, so I'm telling you, child") people generally do not understand that the whole point of secrets is that at least two parties know, which means you might always be betrayed by somebody you think is keeping your secret. For a private key it's easy, don't tell anybody, nobody knows, you can't be betrayed, done.

            For example Hacker News learns my password to this web site every single time I sign in because that's just a secret. We've known how to do better for decades but only a handful of systems I use (e.g. Google) do so and all of them have a "traditional" password option which is like discovering your aeroplane still has a smoking section in 2026.

            1. fc417fc802 · 1789642138 · focus · HN ↗

               I don't see the issue. Attacking a physical lock as you suggest is analogous here to breaking the cryptography in some way. So the NSA busts out its sooper sekrit quantum computer ...

               The inability to betray is a sharp observation but I think the analogy still holds flawlessly. It's a physical lock that you haven't handed out the key for so you're the only one with access to it. However the public counterpart still defies easy explanation.

               Why did you put "symmetric keys" in scare quotes? Is that not the common term in your neck of the woods when speaking about symmetric crypto?

               1. TeMPOraL · 1789662470 · focus · HN ↗

                  Again, the "lock" part is the dumb part.

                  Encryption scrambles the data. Key is the piece of information that lets the information be scrambled in specific way so that it can be unscrambled by someone in possession of the same (symmetric) or complementary (asymmetric) key.

                  The only "lock" in the whole thing is the scrambler (encryption software), and that one is usually publicly known and available.

                  Obvious way to make this clear: if "keys" were a lock, the original data in readable form would be there, accessible if you found a way to bypass or destroy the lock. The whole point of encryption as opposed to locking is that you cannot do this, because the data itself is scrambled - and thus you don't even need to ship any "lock", just the scrambled data, because the "lock" is something everyone already has or can procure.

            2. vel0city · 1789649833 · focus · HN ↗

               > the whole point of secrets is that at least two parties know

               This isn't true. If I do something privately by myself and never tell anyone it's still a secret. If I have a hidden compartment in my desk to hide things and I'm the only one who knows about it, it's a "secret compartment". A secret doesn't have to involve a second party at all.

               1. gowld · 1789660970 · focus · HN ↗

                  And in fact, we have a dedicated term for shared secrets
            3. bigfishrunning · 1789673448 · focus · HN ↗

               > For example Hacker News learns my password to this web site every single time I sign in because that's just a secret.

               I don't know the details of the login system for Hacker News, but i would expect they learn "a hash of your password and some salt" for every login, and your password isn't just transmitted to them. If they're doing things correctly, they're only storing a hash of your password, and can't work backward to get it -- that's a big If, and lots of places get it wrong.

               1. DaSHacka · 1789678434 · focus · HN ↗

                  I've never actually found a site that computes the hash client-side and sends the finished hash to the server, the vast majority just send the regular password to the backend to be hashed and compared (and HN is no exception).

                  And if you think about it, there's really no advantage to sending the hash every time anyway. An attacker that MITMs your traffic once can just resend the static post-computed hash to the backend anyway.

                  The only advantage would be preventing an attacker from seeing a password string you may re-use for other sites, but so long as it's unique for HN alone (surely we all use password managers on here? :-) ) it doesn't matter.

               2. tialaramex · 1789684853 · focus · HN ↗

                  > I don't know the details of the login system for Hacker News, but i would expect they learn "a hash of your password and some salt" for every login

                  No. That would be a terrible idea and so that's not what they do. You can go see for yourself, it's an HTML form, the text field with your password in it is submitted to their web server, much in the same way this larger field full of comment text was sent.

                  If you think a bit harder you'll realize why your approach would be a bad idea. A bad guy who has obtained the password hashes (for example by dumpster diving, or an SQL extraction) can just play back a hash they've seen without ever knowing your password, you've rendered the knowledge of the password useless.

                  Yes, that means if you've been around long enough, sites which had passwords but did not use TLS or before that SSL, were sending your actual password, unencrypted, for any snoop to see. That might seem crazy, but because I'm an old man when I first used the Internet it was normal to send your password, letter by letter in plain text, to connect to a remote Unix machine. The "Secure Shell" you take for granted today did not exist until July 1995.

                  1. fc417fc802 · 1789687790 · focus · HN ↗

                     That's not a bad idea and I believe it is how any modern not-a-website password based authentication works. Agreed that it does not address the attack vector of someone sniffing your password for site A and then logging into site A with it. However a key stretching algorithm (as opposed to just a hash) combined with salt does protect against an attacker logging into site B if the user reused his password.

                     Of course for a website and assuming TLS then in practice it doesn't make much difference whether the hashing takes place client side or server side since an attacker sitting on the server could presumably serve up a compromised frontend. And without TLS a MITM could again compromise the frontend. But hashing client side does at minimum prevent the service operator from accidentally logging plaintext passwords, and anyway not all services are web apps. An attacker can't trivially change out the frontend if it's an app on my phone.

         2. TeMPOraL · 1789662059 · focus · HN ↗

            It's not perfect for symmetric keys at all, because the fundamental fact about locks and keys is that a lock sits on the outside of the thing you're protecting, attaching to it or to a container in which the thing is placed. Encryption is about directly scrambling the protected thing.

            1. yencabulator · 1789663638 · focus · HN ↗

               The mental model is that encryption is a locked box you can only open with the key.

               1. TeMPOraL · 1789717594 · focus · HN ↗

                  That's a dumb mental model, is what I'm saying. The original sin of cryptography/cybersecurity metaphors.

                  1. yencabulator · 1789741815 · focus · HN ↗

                     Better than calling encryption "scrambling".
                  2. fc417fc802 · 1789756362 · focus · HN ↗

                     What's dumb about it? I'd suggest that it's slightly abstract and argue that there's nothing wrong with that. It fits perfectly and it's readily understandable.

                     For example a VPN connection lends itself to being described as a pipe. That already equates the encapsulating protocol with a physical barrier regardless of the presence of cryptography.

                     I think you're just being overly literal, something which will kill almost any decent analogy regardless of topic.

                     1. TeMPOraL · 1789768924 · focus · HN ↗

                        You have a very large subthread debating downstream confusions, which were previously debated in millions of such discussion on-line too. It's a confusion everyone has to learn to live with when first exposed to concept and the metaphor of "keys" and "locks".

                        And it's because it does not fit. Locks and keys are distinct kinds of objects, and are external to the thing being protected, with lock itself being attached to the thing being protected. Only the key can be distributed separately and copied; you come into possession of the security mechanism and the protected object together, they're literally unseparable (that's the point - if you can separate the lock from the thing, you don't need the key anymore).

                        Encryption in contrast is (reversibly) destroying the thing being protected, the "locking mechanism" is public and same for everyone and therefore you already have a copy, and you can't "bypass" it because the very thing being protected has been destroyed (scrambled) and you cannot undo that without having the "key".

                        There's no 1:1 mapping of any concept from physical locks and keys to encryption. It's a fundamentally dumb analogy that people run away with, because at first look it seems to have some semantic similarities.

                        1. yencabulator · 1789770804 · focus · HN ↗

                           "Undo" a "destroy" is just a bad metaphor okay?
      2. fragmede · 1789624854 · focus · HN ↗

         Or how about we call it the lock. There's the (private) key, and it fits the lock (public key). You can pass the lock around, but you need the (private) key to be useful.

         1. danw1979 · 1789627888 · focus · HN ↗

            I dunno if that works or is any less confusing, to be honest.

            I don’t think there’s any process or entity in the physical world that is reasonably familiar to most people that is even remotely suitable as an analogy to public key cryptography.

            1. tialaramex · 1789637052 · focus · HN ↗

               I think this is worth highlighting. Public Key Cryptography is a surprising idea. Like Computation, if you'd told a 19th century mathematician about this, they might buy it as a concept but deem it unlikely to ever happen in practice or be of any significance, in the 20th century these were both realised and caused a massive change to our society.

               These are not analogs to things ordinary people had already seen. For Computation we just got used to it being everywhere and so we don't need to explain it so much.

            2. raddan · 1789642675 · focus · HN ↗

               For what it’s worth, it’s the analogy I use, and for the twenty or so college sophomores I taught on Tuesday, the analogy is sufficiently understandable that they were able to generate and use SSH key pairs to do their homework.

               I think the reason we (the HN crowd) don’t like it is that the analogy starts to break down when you start thinking through all of the operations you can do with public keys. But this does not matter much for somebody learning to use them for the first time. I’ve had to grow comfortable with the idea of giving people imperfect explanations so that they can build an intuition. Once that happens I can return with the mathematics so that they can really understand what is going on.

               1. faxmeyourcode · 1789645568 · focus · HN ↗

                  This analogy is exactly what made it click when I was a teenager.
         2. Reubachi · 1789649316 · focus · HN ↗

            More people being exposed to asymetric keys probably leads to some confusion when imagining the public keys roll as lock in a symetric system.

            IE; the existence of the asymetry allows for the public key to function more than just a "lock", but a much more easy to rationalize "signer attestation.

         3. TeMPOraL · 1789661507 · focus · HN ↗

            Except it makes no sense if you look at the thing, because then you realize that the "lock" and "key" are literally the same thing. In the real world, the lock and the key are completely different objects - there's no way to confuse which is which (and there's no way for one to act as the other if you use them in opposite order, either).

            The analogy doesn't make sense because it's skipping the existence of the third thing that's the actual (pad)lock - the encryption/decryption software. And it does that because it wants to talk about data as having the property of being "locked", which makes no sense in the first place, but that one isn't immediately obvious.

            The whole analogy of locks and keys fundamentally makes no sense when talking about data, because locks are external devices, attached to or directly containing the protected thing, while encryption is the process of scrambling the very thing being protected.

            All confusion stems from this bad choice of analogy, trying to "make it simple" for the normies.

      3. SilasX · 1789625237 · focus · HN ↗

         Yeah, that always bothered me about the terminology. My fix would be to call it a lock -- everyone understands that you can share those and it doesn't make them any easier to open.

         1. morsch · 1789625874 · focus · HN ↗

            That analogy works for encryption but doesn't really work for signature verification

            1. snmx999 · 1789636544 · focus · HN ↗

               Maybe we should not use analogies? Just call them secret-text and public-text.

               1. benjaminjt · 1789640086 · focus · HN ↗

                  Agree. Even just “secret” would be fine for the private key. Maybe pair it with “identity” or “id”.
               2. gowld · 1789661014 · focus · HN ↗

                  "public-text" doesn't describe the purpose of a public key.
            2. SilasX · 1789660910 · focus · HN ↗

               Sure, but you generally those are separate conversations in which you don't need to appeal to the duality of encryption and authentication or apply the analogy to the latter.
      4. [deleted] · 1789645500 · focus · HN ↗

         [deleted]

      5. VorpalWay · 1789649547 · focus · HN ↗

         An alternative way to think about it would be a padlock and a key. Anyone can close the padlock (assuming the common spring loaded design), but only the key holder can open it.

         While this works for encryption, it doesn't really work for explaining signatures or however. Maybe someone can come up with a good analogy for that case.

         1. waltbosz · 1789654913 · focus · HN ↗

            That's the analogy I was taught in college. The public key is really a padlock that had infinite number of copies, but there was only one key that could open all the padlocks. If someone wanted to send a secret message to the person who owned the key, the would obtain a copy of the padlock, put their message in a box and lock it with the padlock, then send the box to the key owner. The key owner was the only person who could unlock the box and read the message.
         2. TeMPOraL · 1789660399 · focus · HN ↗

            Certificate and signature could work as an analogy for public keys, if they weren't already taken by higher level concepts.
      6. cpburns2009 · 1789650148 · focus · HN ↗

         That actually never occurred to me. But it makes sense non-technical people would be skeptical of sharing a public "key". I like public address better than lock (I think lock just adds confusion).
      7. throw0101c · 1789651513 · focus · HN ↗

         > Think about it, the key analogy is just terrible.

         Because originally it was not really that much of an analogy: we only had what is now called "'symmetrical' encryption", but was just "encryption" back in the day (dating back to even Caesar perhaps). So the 'key idea' made complete sense: don't lose the one thing that could unlock things.

         It was only more recently (in the relative, historical sense (~1970s)) that public and private "keys" became a thing, and the differentiation between symmetrical and asymmetrical encryption was made/invented.

         1. TeMPOraL · 1789661189 · focus · HN ↗

            The problem is arguably the symmetry in asymmetrical encryption - namely both "private" and "public" key are the same thing; the labeling "public" vs. "private" reflects your arbitrary choice of which of one you give away, and which one you keep for yourself.

            It's surprising that we didn't invent any kind of physical padlock that accepts two keys, with the lock mechanism such that, when locked with one of the two keys, can only be unlocked by the other key. I can imagine obvious use cases for that, e.g. in shipping, but I guess this won't adopted because it makes the key management problem immediately obvious. But should such a thing existed, that would be the best (edit: just better - see my other comment explaining why "lock" is the dumb part here) analogy to draw terminology from.

            1. SoftTalker · 1789661475 · focus · HN ↗

               We did/do have that kind of lock: A safe deposit box at a bank. To open it, you need two keys, one of which you have and one of which the bank has.

               1. TeMPOraL · 1789661897 · focus · HN ↗

                  But that's the "you need two keys at the same time" case, which is different. I'm talking about "each of them can lock alone, but once locked, only the other one can unlock".

                  The real problem is that lock and key is a fundamentally dumb analogy for a process that scrambles something.

            2. throw0101c · 1789664719 · focus · HN ↗

               > It's surprising that we didn't invent any kind of physical padlock that accepts two keys, with the lock mechanism such that, when locked with one of the two keys, can only be unlocked by the other key.

               They do:

               * <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=VAriLDgpnY8" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=VAriLDgpnY8

               As mentioned in the video they&#x27;re usually used in commercial settings. Also:

               &gt; One Way Cylinder Keying: Allows for the issuance of one key that can ONLY lock, one key that can ONLY unlock and one key that can BOTH lock and unlock the cylinder. Perfect for applications where one key holder should only have authorization to lock, while another should only have authorization to open and yet another can have the authorization to perform both functions. One way keyed products are supplied with 2 nylon head cut keys per product and 1 key order card per product.

               * <a href="https:&#x2F;&#x2F;mangionelocksmiths.com&#x2F;wp-content&#x2F;uploads&#x2F;2017&#x2F;02&#x2F;Mul-T-Lock-USA-complete-book-2016-email.pdf" rel="nofollow">https:&#x2F;&#x2F;mangionelocksmiths.com&#x2F;wp-content&#x2F;uploads&#x2F;2017&#x2F;02&#x2F;Mu...

            3. zzo38computer · 1789666092 · focus · HN ↗

               &gt; namely both &quot;private&quot; and &quot;public&quot; key are the same thing; the labeling &quot;public&quot; vs. &quot;private&quot; reflects your arbitrary choice of which of one you give away, and which one you keep for yourself.

               It is not quite arbitrary. With RSA, you could potentially store only the modulus and the exponents, publishing one exponent and keeping the other one private (or making each privately known to different people, with both having the modulus). However, the way it is commonly stored is with the private key file includes both exponents and several other numbers, and the public exponent is usually 65537 which makes it easy to guess so you cannot effectively keep it secret. With some other kinds of cryptography (other than RSA), you can figure out the public key from the private key even without doing things like this.

            4. DaSHacka · 1789679244 · focus · HN ↗

               &gt; It&#x27;s surprising that we didn&#x27;t invent any kind of physical padlock that accepts two keys, with the lock mechanism such that, when locked with one of the two keys, can only be unlocked by the other key.

               Key exchange blocks are basically this, except one of the two keys is perpetually locked inside the keyblock, and you must use the other to retrieve it (whereupon the key you just used is now locked in the block).

               So not quite the same thing, but the closest example I know of.

      8. upofadown · 1789664435 · focus · HN ↗

         Well most people don&#x27;t verify identity with some sort of physical key. So it doesn&#x27;t work as an analogy in the first place for signatures...

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