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Cryptography Expert Sounds Alarm At Possible Math Hack
netbuzz writes "First we learn from Bruce Schneier that the NSA may have left itself a secret back door in an officially sanctioned cryptographic random-number generator. Now Adi Shamir is warning that a math error unknown to a chip makers but discovered by a tech-savvy terrorist could lead to serious consequences, too. Remember the Intel blunder of 1996? 'Mr. Shamir wrote that if an intelligence organization discovered a math error in a widely used chip, then security software on a PC with that chip could be "trivially broken with a single chosen message." Executing the attack would require only knowledge of the math flaw and the ability to send a "poisoned" encrypted message to a protected computer, he wrote. It would then be possible to compute the value of the secret key used by the targeted system.'"
The problem with backdoors, is that noone can guarantee who uses them. While it allows for (possibly) justified surveillance by our government, it also allows for it by others.
The United States, or the NSA, doesn't have all the world's best cryptographers. Russia, China, etc, other nations have excellent skill in these endeavors. Ironically, by trying to protect the nation, the NSA runs the risk of opening us up to foreign espionage.
TFA is just a summary of an article yesterday in the NYT: http://www.nytimes.com/2007/11/17/technology/17code.html?ref=technology
It seems to me that the most likely source of a math error is in the floating point unit, since floating point math is far more complex than integer math. I've always understood that most crypto is based on integer math, both because it's based on number theory and because floating point math isn't exact. Doesn't that make this sort of exploit extremely unlikely?
Wouldn't pulling off something like this require a level of knowledge and togetherness more in line with a government agency, rather than a "terrorist" group? The results would also be more in line with what a government agency would want ("we have your secrets, ha!"), rather than what a terrorist would want ("Maybe I can't blow up a bridge / poison your water supply / whatever. But then maybe I can. So while you're deciding whether to go do things or hide under your bed all day, I have a question for you: do you feel lucky?").
Why does everything have to come back to terrorists? They kill a small number of people and people go nuts about them. Hunger, disease, motor cars, lightning, ... All these things have killed far more people than terrorists and they don't get brought up at every *FUCKING* opportunity. Yeah. I'm pissed off. If the terrorism obsessed turned on their brains for a picosecond they might realise that they have caused far more damage than any terrorist has.
Um, no. "The terrorists" (a pretty vauge term but I'm assuming you mean those from middle eastern countries by the way you're wording your statement) don't give a rat's ass how we live, whether we have free elections or live with an oppressive government nor do they really care much about how we go about our daily lives, etc, etc. The terrorists wants the US and western countries to stop fucking around in their countries- supporting/installing dictatorships that happen to ally with our interests while bombing and invading countries that we don't like, setting up permanent military bases and just generally exerting our will on them. After a few generations of having western powers screw with their countries and lives it should be little wonder we're not well liked.
Of course, if you were refering to China or someone else then that might be a different story (but again, the wording sounded like someone regurgitating the drivel that gets thrown out by politicians and pundits in the mainstream media).
Terrorists want us to stop screwing around in the Middle East and Central Asia -- specifically they want us to stop supporting Israel and to stop propping up various dictatorships in countries where there'd be a good chance of overthrowing the government and creating a theocracy.
They don't give a flying f--- about "our freedoms" except where they think that shows we are "morally corrupt." Islamic militants are under no illusions that they're going to change our culture any time soon, though. They've got bigger fish to fry back home trying to establish a power block.
How we govern ourselves beyond our foreign policy is utterly unimportant to their larger goals.
If it's for-profit but free, you're not the customer -- you're the product (e.g., the Slashdot Beta's "audience").
I can't see any way for an attacker to utilize a math error in a decryption function
Actually this is a common attack scenario in security protocol analysis. While it does not always happen in real life there are ways it can occur. For example, you try to decrypt the message and get garbage. So what do you do? You send the garbage back to the guy, saying, I couldn't read your message, all I got was this junk. Now you have been tricked into acting as what is called an "oracle" for the decryption function. This opens up a number of attacks which is why the best cryptosystems are immune to such problems.
Want the citizens to give up some freedom/pay some new tax/whatever? Easy! Play the terrorism trump card.
Without some Evil Empire force (that the US plays so well), it is very hard for terrorists to get the emotions going either. Terrorists & empire building governments need each other.
Engineering is the art of compromise.
Who are the "National Safety Administration"?
They're the sister outfit to the "National Highway Traffic Security Administration".
The higher the technology, the sharper that two-edged sword.
The flaw seems too obvious to really have been something illicit. If it was an attempt at a backdoor, it was pretty stupid. And it was a weird/improbable way to create a backdoor -- it was PRNG, not really a cryptographic function per se, and while knowing its output could help you break a system, it wouldn't guarantee it. The people at the NSA had to know it would be combed over.
But the fact that it seems to be incompetence rather than malice doesn't make me feel a whole lot better. There are still a bunch of secret-algorithm ciphers around and in use (and which the government, in its infinite wisdom, treats as more secure than the openly-reviewed ones), that the NSA is basically the only organization that has any access to. If they could miss such a trivial flaw in a PRNG that they knew was going to go out for public scrutiny, what could they have let slip by in a cryptographic function that was supposed to be a state secret?
"Ladies and gentlemen, my killbot features Lotus Notes and a machine gun. It is the finest available."
Comment removed based on user account deletion
Most chips have flaws of one kind or another. Most of these are trivial and can be worked around in microcode. The article mentions the Pentium floating point bug. This caused the original Pentium to return the wrong result for some calculations. In theory, it would be possible to produce a cyphertext that would generate this error if the key contained one of the two values that you needed to generate the error. This then lets you dramatically reduce the key search space.
Other CPU flaws are more serious. There are a few in the Core 2 which allow a process to violate the page protection mechanism, for example. If an attacker found one that caused the program counter to be modified as a side effect of an arithmetic operation then they could create a cyphertext which contained a program at the end and some data at the beginning that caused execution to jump into the exploit code. This is much easier for cypertexts than arbitrary data because the attacker has can make some good guesses about how a cyphertext will be processed.
It seems like this is a very theoretical category of vulnerability to use for anything more than a DoS. On the other hand, as Theo de Raadt says, the only difference between a bug and a vulnerability is the intelligence of your attacker.
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In that case, the benefit of open review (that, just possibly, someone in the small pool of non-spook cryptographers who know what they're doing might find a flaw) is far less than the downside (that your opponents get to see what a modern code system looks like). The lowdown on a modern close-world cipher system would reveal attacks they are defending against, give a good impression of their real capabilities and so on. Yes, in a real shooting war, the spooks have to allow for their crypto systems falling into the wrong hands. But in the current climate, the tactical stuff will be exposed, but the strategic stuff can be closed algorithms and closed keys: what's not to like?
This reminds us all of the S Box hoo-hah, where elaborate theories were put forward by open community `experts' about the `flaws' in the S Boxes in DES. It turned out, of course, that they were optimal against an attack that wasn't even public, and close to optimal against other attacks that (allegedly) weren't known to anyone. I'd take a cipher system that the NSA or GCHQ approves for government use over anything advocated outside the wire., simply because the chances of an intentional weakness in the former are far smaller than the chances of an accidental weakness in the latter.
We went through all this is the discussion about the S Boxes