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I don't see how this is a substantive reply. Yes, once your key is known you no longer have security. That's true regardless of how many keys your scheme employ

I don't see how this is a substantive reply. Yes, once your key is known you no longer have security. That's true regardless of how many keys your scheme employs. Just like in traditional encryption scenarios, your personal key remaining secret is a part of the assumption. That there are now two secret keys doesn't alter the analysis substantially.

AnthonyMouse 9y ago
> Just like in traditional encryption scenarios, your personal key remaining secret is a part of the assumption. That there are now two secret keys doesn't alter the analysis substantially. Of course it does. At best it doubles the risk of key compromise, but it's really much worse than that. A master key isn't like a normal key. If you compromise Alice and Bob's key, you can spy on Alice and Bob, but not Alice and Carol and definitely not Carol and Dan. The existence of a master key is a massive security risk. Alice and Bob's key is worth say $5000. The value of stealing it generally isn't worth the effort. Nobody sends Mossad to spy on every plain old Alice and Bob. A master key for everything is worth trillions of dollars. Every government and crime family would throw everything they have at stealing it, and many of them would succeed. Spetsnaz units and foreign intelligence operatives would fall out of the sky. Crime bosses would pay multi-million dollar bribes and still turn a huge profit. And from there it would leak. It's a completely different level of risk. Orders of magnitude worse. And it implies a prohibition on forward secrecy. So when it leaks, Armageddon.
- hackinthebochs 9y ago
  Lets say I grant everything you say about the danger to every Alice and Bob that a master key exists. The question is, can policies be enacted and systems put into place that provide a commensurate amount of security for the risk the backdoor key poses? It seems plausible that it can be. But this is the conversation that needs to happen, not the boneheaded claim that its "mathematically impossible" to have a secure system with a backdoor. It's plausible that a system can be "secure" under appropriate definitions while having such a backdoor mechanism. If the analysis shows its not possible in practice, then that's fine as well. But we have to actually do the analysis.
  - AnthonyMouse 9y ago
    > The question is, can policies be enacted and systems put into place that provide a commensurate amount of security for the risk the backdoor key poses? It seems plausible that it can be. It's plausible that the government can permanently keep a key to every lock secure against every attacker? That is such a ridiculous claim that just skipping right to "no, that's impossible" is a completely reasonable thing to do. But we can do the analysis if you really want to. Look at the other things the government has tried really hard to protect. Nuclear secrets? Nope. https://en.wikipedia.org/wiki/Atomic_spies https://en.wikipedia.org/wiki/Atomic_spies The government has actually lost hydrogen bombs on multiple separate occasions. Not the secrets, the actual live thermonuclear weapons. The things that one of which can turn all of D.C. into radioactive glass. What about all the sensitive information about the people with security clearances? https://en.wikipedia.org/wiki/Office_of_Personnel_Management_data_breach https://en.wikipedia.org/wiki/Office_of_Personnel_Management... Incredibly dangerous biological materials ("arguably the most deadly disease ever to affect mankind")? https://www.npr.org/2014/07/08/329884145/in-a-lab-store-room-an-unsettling-surprise-lost-vials-of-smallpox https://www.npr.org/2014/07/08/329884145/in-a-lab-store-room... Classified information in general? The list of violations is too long to even enumerate. And this is what happens when the thing they're supposed to be protecting doesn't have incomprehensibly large commercial value on the black market. There is no question that they are not capable of doing this.
    - hackinthebochs 9y ago
      This is just lazy. A string of bits that only need to be accessed behind closed doors isn't like any of those other things. What's more, that secret room can be secured arbitrarily well.
      - AnthonyMouse 9y ago
        Most of those other things are a string of bits that only needs to be accessed behind closed doors. And it's not like a smallpox lab is open to the public either. You can devise a defense against any attack you can think of, but for a trillion dollar prize someone will find an attack you didn't think of. And that's the problem. You can say the words "secured arbitrarily well" but in practice you've created a room with the keys to the world in it and your first indication that your security was insufficient is an incalculable catastrophe. It's like creating a button that gives anyone who presses it three wishes but destroys North America. "Don't worry, we'll put some guards around it" doesn't cut it. Some things need to just not exist.
cesarb 9y ago
> That there are now two secret keys doesn't alter the analysis substantially. It doesn't, and that's the point. There are no "separate levels" of security. The attacker only has to break one of the keys, whichever is the weakest one. The "security level" of the whole system is the "security level" of its least secure part.

AnthonyMouse 9y ago

> Just like in traditional encryption scenarios, your personal key remaining secret is a part of the assumption. That there are now two secret keys doesn't alter the analysis substantially. Of course it does. At best it doubles the risk of key compromise, but it's really much worse than that. A master key isn't like a normal key. If you compromise Alice and Bob's key, you can spy on Alice and Bob, but not Alice and Carol and definitely not Carol and Dan. The existence of a master key is a massive security risk. Alice and Bob's key is worth say $5000. The value of stealing it generally isn't worth the effort. Nobody sends Mossad to spy on every plain old Alice and Bob. A master key for everything is worth trillions of dollars. Every government and crime family would throw everything they have at stealing it, and many of them would succeed. Spetsnaz units and foreign intelligence operatives would fall out of the sky. Crime bosses would pay multi-million dollar bribes and still turn a huge profit. And from there it would leak. It's a completely different level of risk. Orders of magnitude worse. And it implies a prohibition on forward secrecy. So when it leaks, Armageddon.

hackinthebochs 9y ago
Lets say I grant everything you say about the danger to every Alice and Bob that a master key exists. The question is, can policies be enacted and systems put into place that provide a commensurate amount of security for the risk the backdoor key poses? It seems plausible that it can be. But this is the conversation that needs to happen, not the boneheaded claim that its "mathematically impossible" to have a secure system with a backdoor. It's plausible that a system can be "secure" under appropriate definitions while having such a backdoor mechanism. If the analysis shows its not possible in practice, then that's fine as well. But we have to actually do the analysis.
- AnthonyMouse 9y ago
  > The question is, can policies be enacted and systems put into place that provide a commensurate amount of security for the risk the backdoor key poses? It seems plausible that it can be. It's plausible that the government can permanently keep a key to every lock secure against every attacker? That is such a ridiculous claim that just skipping right to "no, that's impossible" is a completely reasonable thing to do. But we can do the analysis if you really want to. Look at the other things the government has tried really hard to protect. Nuclear secrets? Nope. https://en.wikipedia.org/wiki/Atomic_spies https://en.wikipedia.org/wiki/Atomic_spies The government has actually lost hydrogen bombs on multiple separate occasions. Not the secrets, the actual live thermonuclear weapons. The things that one of which can turn all of D.C. into radioactive glass. What about all the sensitive information about the people with security clearances? https://en.wikipedia.org/wiki/Office_of_Personnel_Management_data_breach https://en.wikipedia.org/wiki/Office_of_Personnel_Management... Incredibly dangerous biological materials ("arguably the most deadly disease ever to affect mankind")? https://www.npr.org/2014/07/08/329884145/in-a-lab-store-room-an-unsettling-surprise-lost-vials-of-smallpox https://www.npr.org/2014/07/08/329884145/in-a-lab-store-room... Classified information in general? The list of violations is too long to even enumerate. And this is what happens when the thing they're supposed to be protecting doesn't have incomprehensibly large commercial value on the black market. There is no question that they are not capable of doing this.
  - hackinthebochs 9y ago
    This is just lazy. A string of bits that only need to be accessed behind closed doors isn't like any of those other things. What's more, that secret room can be secured arbitrarily well.
    - AnthonyMouse 9y ago
      Most of those other things are a string of bits that only needs to be accessed behind closed doors. And it's not like a smallpox lab is open to the public either. You can devise a defense against any attack you can think of, but for a trillion dollar prize someone will find an attack you didn't think of. And that's the problem. You can say the words "secured arbitrarily well" but in practice you've created a room with the keys to the world in it and your first indication that your security was insufficient is an incalculable catastrophe. It's like creating a button that gives anyone who presses it three wishes but destroys North America. "Don't worry, we'll put some guards around it" doesn't cut it. Some things need to just not exist.

cesarb 9y ago

> That there are now two secret keys doesn't alter the analysis substantially. It doesn't, and that's the point. There are no "separate levels" of security. The attacker only has to break one of the keys, whichever is the weakest one. The "security level" of the whole system is the "security level" of its least secure part.