4 ms·

Barr's crypto backdoor claim is a fallacy, which I'll show with math

29 points by miles 7y ago

twothamendment 7y ago
Math won't change his mind (or other politicians). I think they already know what they can do with a backdoor and why it is bad. I don't think they care.
the_snooze 7y ago
"Keys Under Doormats" should be required reading on the issue of exceptional access. https://www.schneier.com/academic/paperfiles/paper-keys-under-doormats-CSAIL.pdf https://www.schneier.com/academic/paperfiles/paper-keys-unde... tl;dr Governments are vague about what they actually require in terms of exceptional access. And few ever discuss how to mitigate the inevitable multi-jurisdiction conflicts, like if China compels Apple to unlock phones belonging to US-friendly intelligence assets.
tessierashpool 7y ago
Barr and others like him have been saying this stuff for decades. Showing them the math has limited utility. Geeks have been doing that for decades too, with limited results. Barr and his predecessors don't read math, they wouldn't understand it if they did, and even if they understood it, they would demand backdoors anyway. Barr in particular has already demonstrated that national security and our economy are less important to him than increased power. It's probably true of all these government people making all these false claims about cryptography since the mid 1990s, but it's demonstrably true of Barr. (The Trump coverup he's currently attempting is not even his first coverup as Attorney General. He did similar work for a previous administration.)
admax88q 7y ago
There are other means of backdooring rather than setting key size. I'm not saying its a good idea, but there are means to make cryptosystems that are breakable by the NSA but not anyone else. Consider the concerns around the Dual_EC random number generator that was pushed by the NSA. People believe that the NSA has a backdoor into that random number generator due to how the constants were generated. There are similar concerns for various ECC curves. So the government could mandate that industry uses their specific RNG or specific ECC curves. Effectively giving them a backdoor that nobody else has. It's disingenuous to argue its a bad idea because its impossible to build. It's also a bad argument strategy, as once someone learns that it can be built they will assume that you're lying to push your agenda and not trust further arguments you put forward.
- UncleEntity 7y ago
  > Effectively giving them a backdoor that nobody else has. Until they do...then you go from 100% to 0% as TFA states. All it takes is someone figuring out how the NSA generated their magic constants (which obviously contain a flaw) and its game over.
  - admax88q 7y ago
    Sure but that's not the argument that the article made. Thats an important point to discuss and there may be ways to mitigate the damage of such a compromise (multiple curves, per key escrow). The article made a ridiculous argument for why backdooring is "impossible". Presumably they made it to persuade laypeople but what they really did is misinform laypeople and set them up to be pushed to the other side when they find they've been lied to. Not to mention you're also fucked if an unintentional flaw is discovered in AES or similar. You still need to be able to upgrade you crypto in response to advances in the state of the art, or leakage of important secrets.
- credit_guy 7y ago
  > So the government could mandate that industry uses their specific RNG or specific ECC curves. Effectively giving them a backdoor that nobody else has. I guess you are advocating for security by obscurity here (security in this case being the security of the backdoor). Not so good. But here's an alternative. The government can mandate that each time you send an encrypted message, you send another encrypted copy. The first one uses your addressee's public key, the latter the NSA's public key. It's not particularly elegant, but it does the job. It's not 99% secure, it's 100% secure.
- subjectsigma 7y ago
  I don't know enough about crypto to know if specific curves would work, but why couldn't somebody just guess/leak the curve they're using and ruin the whole thing? What the Twitter post truly doesn't address is key escrow, which is still extremely dangerous but seemingly crypto-sound. It's not impossible to build the system just a really, really bad idea. >It's disingenuous to argue its a bad idea because its impossible to build. I think this is a really key point. I hate the idea of govt backdoors as much as anyone, but we shouldn't need to win by misleading, even with good intentions. People can understand that the government is trying to fuck them over without hand waving.
deogeo 7y ago
I see the focus on practicality as a bit misguided. Even if it could be done, giving the government (and its friends) covert access to all information is dystopian. Looking at the recent history of pretty much any country (including the US, let alone Russia or China, or North Korea) should show what a terrible idea this is. Edit: It wouldn't even improve safety. Imagine how convenient it would be for the military-industrial-prison complex to know everything about every anti-war activist. The increased oppressive capacity would more than make up for any decrease in crime. That's all assuming Americans have turned fully utilitarian, and discarded any pesky ideals such as 'freedom' that might further tilt this analysis.
asdkhadsj 7y ago
A lot of people here commenting on how Barr won't care/etc. I don't see that as the point for this discussion. In my view; If "we"[1] are to win, these types of information sharing/etc posts are essential. As commenters have pointed out, Barr won't care about this logic. In fact, there is no logic that Barr and his ilk will care about. Yet there are hundreds of thousands of people who simply have no idea. They are not uncaring or malicious, crypto is a complex topic and they're not computer people. Barr and his group will (and have!) spin crypto to be something terrorists and pedophiles solely use to get away with evil. We need to have equal, if not greater, "counter spin" to at least combat the propaganda. Call it educating the public or call it propaganda, it doesn't matter. We may not win if we publish articles like this, but we will certainly lose if "we" are the only ones that care about this topic. When the game is played on such a large scale we can't depend on people being informed, we need to bring people information. I don't intend to discuss how effective information on this subject will be to the "common" person; but I think we need to try. Lest we lose crypto with thunderous applause. [1]: People who care about crypto and privacy/etc. edit: Many typos. Coffee, save me.

29 points by miles 7y ago

Math won't change his mind (or other politicians). I think they already know what they can do with a backdoor and why it is bad. I don't think they care.

the_snooze 7y ago

"Keys Under Doormats" should be required reading on the issue of exceptional access. https://www.schneier.com/academic/paperfiles/paper-keys-under-doormats-CSAIL.pdf https://www.schneier.com/academic/paperfiles/paper-keys-unde... tl;dr Governments are vague about what they actually require in terms of exceptional access. And few ever discuss how to mitigate the inevitable multi-jurisdiction conflicts, like if China compels Apple to unlock phones belonging to US-friendly intelligence assets.

tessierashpool 7y ago

Barr and others like him have been saying this stuff for decades. Showing them the math has limited utility. Geeks have been doing that for decades too, with limited results. Barr and his predecessors don't read math, they wouldn't understand it if they did, and even if they understood it, they would demand backdoors anyway. Barr in particular has already demonstrated that national security and our economy are less important to him than increased power. It's probably true of all these government people making all these false claims about cryptography since the mid 1990s, but it's demonstrably true of Barr. (The Trump coverup he's currently attempting is not even his first coverup as Attorney General. He did similar work for a previous administration.)

admax88q 7y ago

There are other means of backdooring rather than setting key size. I'm not saying its a good idea, but there are means to make cryptosystems that are breakable by the NSA but not anyone else. Consider the concerns around the Dual_EC random number generator that was pushed by the NSA. People believe that the NSA has a backdoor into that random number generator due to how the constants were generated. There are similar concerns for various ECC curves. So the government could mandate that industry uses their specific RNG or specific ECC curves. Effectively giving them a backdoor that nobody else has. It's disingenuous to argue its a bad idea because its impossible to build. It's also a bad argument strategy, as once someone learns that it can be built they will assume that you're lying to push your agenda and not trust further arguments you put forward.

UncleEntity 7y ago
> Effectively giving them a backdoor that nobody else has. Until they do...then you go from 100% to 0% as TFA states. All it takes is someone figuring out how the NSA generated their magic constants (which obviously contain a flaw) and its game over.
- admax88q 7y ago
  Sure but that's not the argument that the article made. Thats an important point to discuss and there may be ways to mitigate the damage of such a compromise (multiple curves, per key escrow). The article made a ridiculous argument for why backdooring is "impossible". Presumably they made it to persuade laypeople but what they really did is misinform laypeople and set them up to be pushed to the other side when they find they've been lied to. Not to mention you're also fucked if an unintentional flaw is discovered in AES or similar. You still need to be able to upgrade you crypto in response to advances in the state of the art, or leakage of important secrets.
credit_guy 7y ago
> So the government could mandate that industry uses their specific RNG or specific ECC curves. Effectively giving them a backdoor that nobody else has. I guess you are advocating for security by obscurity here (security in this case being the security of the backdoor). Not so good. But here's an alternative. The government can mandate that each time you send an encrypted message, you send another encrypted copy. The first one uses your addressee's public key, the latter the NSA's public key. It's not particularly elegant, but it does the job. It's not 99% secure, it's 100% secure.
subjectsigma 7y ago
I don't know enough about crypto to know if specific curves would work, but why couldn't somebody just guess/leak the curve they're using and ruin the whole thing? What the Twitter post truly doesn't address is key escrow, which is still extremely dangerous but seemingly crypto-sound. It's not impossible to build the system just a really, really bad idea. >It's disingenuous to argue its a bad idea because its impossible to build. I think this is a really key point. I hate the idea of govt backdoors as much as anyone, but we shouldn't need to win by misleading, even with good intentions. People can understand that the government is trying to fuck them over without hand waving.

deogeo 7y ago

I see the focus on practicality as a bit misguided. Even if it could be done, giving the government (and its friends) covert access to all information is dystopian. Looking at the recent history of pretty much any country (including the US, let alone Russia or China, or North Korea) should show what a terrible idea this is. Edit: It wouldn't even improve safety. Imagine how convenient it would be for the military-industrial-prison complex to know everything about every anti-war activist. The increased oppressive capacity would more than make up for any decrease in crime. That's all assuming Americans have turned fully utilitarian, and discarded any pesky ideals such as 'freedom' that might further tilt this analysis.

asdkhadsj 7y ago

A lot of people here commenting on how Barr won't care/etc. I don't see that as the point for this discussion. In my view; If "we"[1] are to win, these types of information sharing/etc posts are essential. As commenters have pointed out, Barr won't care about this logic. In fact, there is no logic that Barr and his ilk will care about. Yet there are hundreds of thousands of people who simply have no idea. They are not uncaring or malicious, crypto is a complex topic and they're not computer people. Barr and his group will (and have!) spin crypto to be something terrorists and pedophiles solely use to get away with evil. We need to have equal, if not greater, "counter spin" to at least combat the propaganda. Call it educating the public or call it propaganda, it doesn't matter. We may not win if we publish articles like this, but we will certainly lose if "we" are the only ones that care about this topic. When the game is played on such a large scale we can't depend on people being informed, we need to bring people information. I don't intend to discuss how effective information on this subject will be to the "common" person; but I think we need to try. Lest we lose crypto with thunderous applause. [1]: People who care about crypto and privacy/etc. edit: Many typos. Coffee, save me.