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Loophole in Windows Random Number Generator
Invisible Pink Unicorn writes "A security loophole in the pseudo-random number generator used by Windows was recently detailed in a paper presented by researchers at the University of Haifa. The team found a way to decipher how the number generator works, and thus compute previous and future encryption keys used by the computer, and eavesdrop on private communication. Their conclusion is that Microsoft needs to improve the way it encodes information. They recommend that Microsoft publish the code of their random number generators as well as of other elements of the Windows security system to enable computer security experts outside Microsoft to evaluate their effectiveness. Although they only checked Windows 2000, they assume that XP and Vista use similar random number generators and may also be vulnerable. The full text of the paper is available in PDF format."
129775, 80123133, 5580012. 6740091, 6558, 42!
The World Wide Web is dying. Soon, we shall have only the Internet.
I assume this is only a problem for those whose motherboard doesn't have a hardware random-number generator?
No, but they might use it for encrypting windows passwords.
Give me Classic Slashdot or give me death!
Whoops -- it's not rand, it's CryptGenRandom.
I am still at a loss to wonder why a PC does not have a white noise generator built into it yet. Even the best random number algorithms are pseudo random, so blasting Microsoft for their algorithm is a little like blasting the kid for not carrying enough of a bucket when the dam is the thing that broke.
Put white noise hardware and real random number hardware on PCs, and this whole problem goes away.
This is my sig.
Your system must meet the requirements to be able to run the Windows Random Number Generator on Vista. Otherwise, you will need to use Windows Number Generator Basic. The only number WNGB can generate is 4.
In other news, Miguel de Icaza said that he believes that the random number generator is a good idea. Linux should have one because Microsoft is going to win anyway, so linux would better be prepared if it doesn't want to be locked out of the future markets, and presented a beta version of the algorithm. Members of the GNOME foundation are participating in the standarization: ''it's better to provide our own insecure random number generator'' said ownen taylor.
From TFA:
Date: received 4 Nov 2007
Old indeed. 8 days. That's a lot, Microsoft might have already fixed it, you see, they fix things fast!
I'm an infovore...
The only benefit that could possibly be derived by publishing algorithms and/or code for Windows security would be if (a) changes proposed would be implemented quickly and (b) everyone planet-wide upgraded.
If both of these did not happen, especially if (b) didn't happen, what you would be doing is exposing all non-upgrading users to the full brunt of whatever flaws their might be. Would this really be productive? Does this remind you of various failures in Linux code that led to rootkits being developed for it. Did the victims of such attacks think it was all for the best because they didn't upgrade in a timely manner?
Yes, relying on people not reverse-engineering code to protect users isn't a great plan. But the current situation - as regrettable as it is - is this is the only plan. There are no fallbacks, there are no alternatives. Most of the running copies of Windows aren't going to be "fixed" in any way whatsoever.
Looks like if you can use their method to find the current state fast enough, windows doesn't do a great job of reseeding very quickly: I read through the PDF and found this comparison of the LRNG to WRNG (p. 18) - "Reseeding timeout. The LRNG is feeding the state with system based entropy in every iteration and whenever system events happen, while the WRNG is reseeding its state only after generating 128 KBytes of output. Synchronization. The collection of entropy in the LRNG is asynchronous: whenever there is an entropy event the data is accumulated in the state of the generator. In the WRNG the entropy is collected only for a short period of time before the state is reseeded. In the long period between reseedings there is no entropy collection. Security implication: The impact of the previous four properties is that forward and backward security attacks are more severe when applied to the WRNG. The attacks are more e±cient by twelve orders of magnitude. They reveal the outputs of the generator between consecutive reseedings, and these reseedings are much more rare in the case of the WRNG. In some cases, reseeding the LRNG happens every few seconds, while the WRNG is reseeded every few days, if it is reseeded at all."
Quiz: True or False -- On a scale of 1 to 10, what is your middle name?
http://xkcd.com/221/
That it will be possible to predict what values Excel will give us in our spreadsheets?
When things get complex, multiply by the complex conjugate.
I wonder if this is a similar problem?
Is there a list of slots machines that run windows?
factor 966971: 966971
You'd think that computers would have built-in hardware based RNGs by now. On-board sound, video, network, etc.......where is the radioactive decay RNG? After all, in 1985 plutonium should be available in every corner drugstore.
I got the idea from a project that used a webcam snapping pictures of a Lava Lamp® as a hardware RNG.
IMO the attack is not so severe as they make it sound. While this is a nice piece of reverse engineering and cryptanalysis, in practice the security implications are small.
The bottom line is that every process has its own copy of the RNG state. That means that breaking into one process will not help you deduce the random numbers being used by another. (The authors comment that there may be similarities between the two states, but they don't have any way to turn that into a practical attack.) So the only thing this does is it lets an attacker who compromises a certain process or program, such as IE, be able to learn the random number state. From that he can deduce old random numbers that were used, as well as deduce new random numbers that will be created in the future.
That second part is hard to avoid, but the first part, running the state backward (confusingly called forward security by cryptographers), is a sign of bad design of the RNG. Okay, Microsoft messed that up. But what are the security implications?
The implication is that if someone breaks into your computer, here is something more he can do. Not only can he take over going forward, he can learn a certain amount of data about the past. If you had an SSL protected session in the past, then he could go back and figure out what they keys were back then and decrypt the data.
But how bad is this, really? Compared to the harm he can already do by breaking into your computer? Given that he's there, he can learn all of your future SSL keys anyway. Anywhere you go in the future, your bank, paypal, ebay, any site he can learn all of your passwords and account numbers. He doesn't need to compromise the RNG for this, he can just watch your keystrokes. Basically, you are totally screwed if this happens.
Given the enormous magnitude of the security lost, the additional harm from being able to decrypt a few old requests is quite small. You are basically owned from then on. If you have insecure software that is vulnerable to such attacks, you're screwed anyway. A weakness in the RNG state means you are slightly more screwed, that's all. It's not a major change in the security equation.
The bottom line is that most of the damage comes from the break-in. Again, not to take anything away from these guys' work, but the attack they describe is at worst just the icing on a very nasty cake. Microsoft should fix it, and it sounds like they probably have in Vista, but nobody needs to change their security practices because of this flaw.