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Comment by userbinator | Hacker News Reader

leaking 15 bits per hour.

Exactly. 15 bits per hour, in an artificial environment with minimised noise, after untold amounts of preparatory work were already performed to analyse the software running on the target machine.

Here, have 15 bytes from a random process running on my machine (I just randomly attached a debugger, scrolled through memory arbitrarily, and copied them):

d1 e1 81 f9 fe ff 00 00 76 05 b9 fe ff 00 00 66 89

What are they? I don't know. Maybe you're really lucky and it's a key to something, or a password hash... but what? The above would've taken 8 hours to read using that attack. Now you should see the level of unconcern I have about this. Someone who is being targeted would care more, but I don't believe me and indeed the majority of users are so important as to be in such a position.

In much the same way I'm not going to install bars over every window of my house.

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15 bits per hour means that in 136 hours you potentially exfiltrate a 2048 private key. Actually make it 120 hours since the rest at that point is bruteforceable.

I imagine Gmail's HTTPS certificate, or a Microsoft code signing key, or Linus' GPG key, or being able to impersonate some government agency or messaging server, are well worth 5 days of this.

Yes, of course as I referred to this is something only high-value targets need to worry about, and even then I think it's not that high up on the list of risks. 5 days is just to read the data, and there's a considerable amount of preparatory work involved in setting up this attack --- figuring out what to read and where it is, is just as hard if not more so than figuring out how to read it through Spectre.

The authors of that paper have the massive advantage of knowing exactly the software running on the target system and its environment; something which an attacker in the real world is unlikely to have, unless the attacker already has such familiarity with the system that it seems far easier to exfiltrate data via some other means than trying to find and setup this very slow side-channel. Everything has to be set up just right for this to work. Otherwise you might probably still manage to read something, but it's completely useless.

(High-value private keys in companies are likely to be in HSMs anyway, in which case they're completely inaccessible to attacks like these.)

Not really. How do you know where that 2048 bit private key is? You might have to read through the entire address space. On a relatively small server with 16 gigabytes of RAM, it'll only take you about a million years to exfiltrate the entire thing...

Let's say you luck out and only need to read the first 100 megabytes of memory... you're talking 1000's of years.

> d1 e1 81 f9 fe ff 00 00 76 05 b9 fe ff 00 00 66 89

That's amazing, I have the same combination on my luggage!

Are you a missileer who is confusing your luggage code with your ICBM missile code?

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