4 ms·

I'm dead sure they aren't using them for anything. This is SF. If they were really used for anything, a random dude in a black hoodie and white SUV can just sm

by dheera 5mo ago

I'm dead sure they aren't using them for anything. This is SF. If they were really used for anything, a random dude in a black hoodie and white SUV can just smash the glass and take down the internet, and the SF police wouldn't do a thing.

kgeist 5mo ago
If you look up videos on YouTube, you'll see that they allow visitors to stand between the lava lamps and the cameras (sometimes even entire groups!). And I've always wondered: doesn't that reduce entropy, since people usually wear monotone clothing? And if the lamps are so important, why would they allow that? Maybe the lamps do contribute something, but their system most likely already generates enough entropy with or without the lamps...
- hekkle 5mo ago
  It also depends on how often samples are taken. If it only occurs every hour, Fred in his white shirt is highly unlikely to be standing in the exact same spot still. Remember, these are only seed values, a pseudorandom number generator will run indefinitely, but from what I understand, CF re-runs these periodically with different seed values, to stop people finding the pattern.
AlotOfReading 5mo ago
Smashing the glass wouldn't make it less effective. The sensor itself has noise, and the camera output is fed into an HMAC with a key based on the current nanosecond before being combined with a traditional entropy source before it ever went anywhere. Even then, it was only used as a seed for the entropy pool on the actual server.
- dheera 5mo ago
  > and the camera output is fed into snip snip ?
  - TZubiri 5mo ago
    If your attack vector is breaking and entering, that's a pretty effective cybersecurity mechanism. But even if it happened, this is one of many additive entropy mechanism, removing or controlling only one source would not be sufficient for any attack.
  - AlotOfReading 5mo ago
    You still wouldn't be about to distinguish the output from noise unless you know the key or you've broken the cryptography, even if you know every bit of the message. Isn't it neat? And yes, as the other comment points out it's only one source among multiple.
Gh0stRAT 5mo ago
It's been quite a while since I first heard about it, but IIRC they were seeding cryptographic PRNGs with entropy from multiple sources, one of which was allegedly this art installation. Seeding PRNGs with sufficiently unpredictable data was a real security concern for a while. New cloud instances have a small entropy pool space for attackers to enumerate due to lack of a real source of randomness. (See the Debian/OpenSSL issue for what can happen when your entropy pool is too small/predictable) One fun fact about XOR is that anything XOR'd with a uniform random distribution results in a uniform random distribution, so there isn't any harm in mixing additional non-attacker-controlled entropy sources in as long as at least one of them is sufficiently unpredictable. The lava lamps provide a potentially hard-to-predict source of entropy for this, but if it's not available then it certainly doesn't "take down the internet". They'll still use packet arrival timing, interrupt timing, etc to seed their CSPRNGs.

by dheera 5mo ago

kgeist 5mo ago

If you look up videos on YouTube, you'll see that they allow visitors to stand between the lava lamps and the cameras (sometimes even entire groups!). And I've always wondered: doesn't that reduce entropy, since people usually wear monotone clothing? And if the lamps are so important, why would they allow that? Maybe the lamps do contribute something, but their system most likely already generates enough entropy with or without the lamps...

hekkle 5mo ago
It also depends on how often samples are taken. If it only occurs every hour, Fred in his white shirt is highly unlikely to be standing in the exact same spot still. Remember, these are only seed values, a pseudorandom number generator will run indefinitely, but from what I understand, CF re-runs these periodically with different seed values, to stop people finding the pattern.

AlotOfReading 5mo ago

Smashing the glass wouldn't make it less effective. The sensor itself has noise, and the camera output is fed into an HMAC with a key based on the current nanosecond before being combined with a traditional entropy source before it ever went anywhere. Even then, it was only used as a seed for the entropy pool on the actual server.

dheera 5mo ago
> and the camera output is fed into snip snip ?
- TZubiri 5mo ago
  If your attack vector is breaking and entering, that's a pretty effective cybersecurity mechanism. But even if it happened, this is one of many additive entropy mechanism, removing or controlling only one source would not be sufficient for any attack.
- AlotOfReading 5mo ago
  You still wouldn't be about to distinguish the output from noise unless you know the key or you've broken the cryptography, even if you know every bit of the message. Isn't it neat? And yes, as the other comment points out it's only one source among multiple.

Gh0stRAT 5mo ago

It's been quite a while since I first heard about it, but IIRC they were seeding cryptographic PRNGs with entropy from multiple sources, one of which was allegedly this art installation. Seeding PRNGs with sufficiently unpredictable data was a real security concern for a while. New cloud instances have a small entropy pool space for attackers to enumerate due to lack of a real source of randomness. (See the Debian/OpenSSL issue for what can happen when your entropy pool is too small/predictable) One fun fact about XOR is that anything XOR'd with a uniform random distribution results in a uniform random distribution, so there isn't any harm in mixing additional non-attacker-controlled entropy sources in as long as at least one of them is sufficiently unpredictable. The lava lamps provide a potentially hard-to-predict source of entropy for this, but if it's not available then it certainly doesn't "take down the internet". They'll still use packet arrival timing, interrupt timing, etc to seed their CSPRNGs.