Still the quote from @ioerror is: "RC4 is broken in real time" so that's either hyperbole or there is an attack better than 75 hours still out there.
> To successfully decrypt a 16-character cookie with a success probability of 94%, roughly 9x2^27 encryptions of the cookie need to be captured. Since we can make the client transmit 4450 requests per seconds, this amount can be collected in merely 75 hours.
How likely would that amount of network traffic and energy consumption cue the potential victim that something malicious is going on?
I guess that 4450 requests/s to one IP, or even spread across multiple IPs, could trigger some alarms if the victim is alert. Unfortunately, I'm not that familiar with IDS/IPS's to answer that with much confidence.
In any case, an attacker has a lot of options. The requests do not need to be made sequentially, so an attacker could basically start and resume his attack whenever he wants, e.g. when the victim is away from keyboard (which he can estimate based on the network traffic someone usually generates). An attacker could also simply slow down the number of requests/s, although this results in a larger number of hours required for a successful attack.
As for energy/CPU consumption, I don't think that'd be a big concern. When the practical attack was performed, the CPU usage went up to around 75%, still allowing one to visit other websites without noticing anything. So unless one would closely monitor the CPU/network usage, I don't think the average victim would notice it.
What if this attack targeted a phone or laptop? Battery would die faster, device would get warmer, and fans spin up.
Why even bring it up?
Do you really think this scenario is realistic and worthy of consideration at all?
I think the bigger issue with this exploit is just the fact that so many submissions need to be sent. I don't really see someone sitting there for 75 hours while this takes place without closing the browser/window/tab.
EDIT: If you're already injecting JS, you're probably better off just phishing the user for their credentials. Faster, easier, and will work more often than relying on the user staying active enough to send traffic for the next 75h.
EDIT 2: Not saying this isn't a valid vulnerability, just not one that can be practically executed currently without much simpler alternatives.
But that's not a problem. If the user closes the browser or tab, the attack can continue at a later point in time. It doesn't need to be collected all at once. As a concrete example, if you leave your computer at work running during the weekend, the attacker has enough time. Or if you leave it running during the night, the attack can be spread out over a few nights. I'm sure there are even more scenarios than just these two examples: there's room for quite some flexibility when performing the attack.
That's assuming the attacker regains control, so you'd have to visit a malicious page every time the attack needs to be re-initiated. EDIT: I'm dumb, somehow I managed to forget mid conversation that this was assuming MitM and not a compromised site. Disregard this point.
Also, while this method can be used for other, static data, pretty much all of the stuff you would want / have access to through doing this will be time-sensitive. Even a straight 72h most "secure" things such as cookies will be changed, forcing a restart of this process. Extending this even longer just gives a bigger window for the cookie/whatever to timeout.
EDIT: though I guess if the cookie you're trying to crack doesn't expire, then this could be an issue. I still think there are vastly easier methods if you can arbitrarily inject into http pages though.
Every non-HTTPS page can be considered malicious, if the attacker can do a MITM.
Since the attacker can capture the encrypted traffic, he most probably is in the middle and can do a MITM.
Therefore, if you are under this attack, every non-HTTPS page is malicious.
Let's say the client leaves their computer on at work over a long weekend ...
The collision attacks against MD5 were at first also claimed to be impractical...
It really shouldn't have been considered a proper cryptographic cypher ever.
Hopefully the NSA MITMs it with an "RC4 is fffiiinnneee" message.
"Only" 75 hours, where you have to force the victim to do make a very large number of encrypted messages. IMO, this wouldn't work when trying to break someone's SSL connection at the local Starbucks.
If I had a dime for every penny of damage caused when people downplay the practicality of attacks against deployed crypto...
75 hours is enough time to attack a laptop left plugged in at the office over a 3-day weekend, and there's no reason why you'd have to attack only one laptop at a time.
The paper also says, "capturing traffic for 52 hours already proved to be sufficient", so it's not like 75 hours is some hard minimum.
"Our attack is not limited to decrypting cookies. Any data or information that is repeatedly encrypted can be recovered."
"We can break a WPA-TKIP network within an hour."
RC4 is dead, dead, dead. As with MD5, the writing's been on the wall for a while now, and attacks are only going to get better.
But if a couple guys can break something in 75 hours, knowing crypto attacks only get better, you can already consider this broken.
Also, 16 characters seems awfully short for a cookie, especially one meant for authentication purposes.