A Timing Attack In Action
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A Timing Attack In Action
1–10 of 18 posts
Re: A Timing Attack In Action
#2Something not mentioned here is that timing attacks have been proven effective even across the internet; you might think "Oh the jitter in TCP is going to overwhelm any leaked information," but you would be wrong.
Re: A Timing Attack In Action
#3How does this work with hashed passwords?
Wouldn't any semblance of avalanche effect make this attack useless?
Re: A Timing Attack In Action
#4Something not mentioned here is that timing attacks have been proven effective even across the internet; you might think "Oh the jitter in TCP is going to overwhelm any leaked information," but you would be wrong.
I do have the sentence "This difference is enough to measure, even on web applications." in the fourth paragraph. Should I highlight that a bit, bold maybe?
I'd also like a good reference for that, and my Google skills were failing me. Do you happen to have a link to something show that off?
Re: A Timing Attack In Action
#5How does this work with hashed passwords? Wouldn't any semblance of avalanche effect make this attack useless?
It can work the same way. You just slowly figure out the hash: this pw for this user was a bit faster than all the other failures, so we know the first byte of the hash is ...
If you have a bunch of hashes precomputed, you can start to figure things out pretty quick.
The point is it's still leaking information about what's going on.
Re: A Timing Attack In Action
#6Something not mentioned here is that timing attacks have been proven effective even across the internet; you might think "Oh the jitter in TCP is going to overwhelm any leaked information," but you would be wrong.
I do have the sentence "This difference is enough to measure, even on web applications." in the fourth paragraph. Should I highlight that a bit, bold maybe? I'd also like a good reference for that, and my Google skills were failing me. Do you happen to have a link to something show that off?
Re: A Timing Attack In Action
#7Something not mentioned here is that timing attacks have been proven effective even across the internet; you might think "Oh the jitter in TCP is going to overwhelm any leaked information," but you would be wrong.
I do have the sentence "This difference is enough to measure, even on web applications." in the fourth paragraph. Should I highlight that a bit, bold maybe? I'd also like a good reference for that, and my Google skills were failing me. Do you happen to have a link to something show that off?
I missed that on the first read-through. Invariably when you introduce someone smart to timing attacks they will say "Oh, but that's not going to be practical over TCP/IP.
Re: A Timing Attack In Action
#8How does this work with hashed passwords? Wouldn't any semblance of avalanche effect make this attack useless?
Hashing would make this technique less useful, but not necessarily useless. For instance, if there is no salt involved, and the hashing algorithm is known (or guessable), you can still make some use of the information leaked.
The difference is that you are not being leaked information about the password, but about the hash of the password. One problem with trying to brute force an authentication over the internet is that it is slow and potentially noticeable by the server admin (then you get cut off). If you exploited a timing attack from a comparison between raw md5's or sha1's of a password, then you can use the leaked information to focus your brute force. Basically, you could use a rainbow table to help you pick what passwords to try next, getting a lot more bang for your buck. In this way you can use the combination of offline brute forcing to generate possible hashes, and the timing attack to select which passwords to actually send.
Now an unknown salt would still ruin your day, just like it is designed to make life difficult for rainbow tables in the first place.
Re: A Timing Attack In Action
#9If you're comparing plain text passwords then you've already done something wrong. You'll find the hash construct mitigates against attacks like these due to its nature, especially with a per user salt.
Re: A Timing Attack In Action
#10How does this work with hashed passwords? Wouldn't any semblance of avalanche effect make this attack useless?
It can work the same way. You just slowly figure out the hash: this pw for this user was a bit faster than all the other failures, so we know the first byte of the hash is ... If you have a bunch of hashes precomputed, you can start to figure things out pretty quick. The point is it's still leaking information about what's going on.
This makes sense, I hadn't thought of knowing the hashing method and it being unsalted. Knowing those it would be just as easy to whittle the list down exactly the same way.