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Your Facebook Pokes Are Stored For Two Days. Encryption Keys Then Deleted
- mikegioia 14y agoI'm still a little confused. It seems the "poke" is encrypted, so they encrypt the picture that's sent. But then the encryption key is deleted. Does that mean the "encrypted photo" is deleted after 2 days, or is the photo's "identification key" (like a hash or ID) deleted after 2 days?
- ConstantineXVI 14y agoThey're (explicitly) deleting the key; provided they're not using ancient or horribly broken encryption, the image itself is effectively indistinguishable from gibberish. I'd assume the images themselves get deleted as well, but without a key they're worthless anyway.
- pyre 14y agoSounds like the photo itself may or may not be deleted, but the keys definitely are. Though the "two days" part is a bit of a misnomer as the key backups exist for 90 days. Even if they are deleting the db copy of the photo, they probably aren't going the whole hog and clearing it out of backups,etc (as mentioned elsewhere) so this is why the keys are relevant.
- sbisker 14y agoWait, my engineer-sense is tingling. Why are they just deleting the key? If they really couldn't access the Poke after deleting the key, wouldn't they want to save storage costs by deleting the encrypted message contents too? Unless, of course, the key isn't the only way the message can be decrypted.
- CJefferson 14y agoMaking sure no pokes end up getting stored on a backup, or in a cache, or temporary directory, could be tricky. Having to only have one thing, stored specially, to clean out might well be easier to organise in a big already existing framework.
- furyofantares 14y agoA backup doesn't make sense without also backing up the key. Caching could make sense without caching the key if the key is way smaller than the data, but why cache something that only needs to be read once?
- carbocation 14y agoI assume they're taking advantage of systems that are already in place, at scale, at Facebook. Then, to ensure that this app has the privacy that people expect from an app of the ephemeral kind, they are baking in additional precautions. In this case, a key that gets destroyed is the precaution. I am not an insider, this is just a guess, etc.
- ConstantineXVI 14y agoIf the designer was particularly paranoid, they could be keeping the keys in RAM only (on machines without swap, of course). If the keys never touch disk, easier to purge them and know they're gone.
- loxs 14y agoI think that they have an extremely durable/redundant data store, which is effectively "write-only". You write to some server that replicates its data to other machines, possibly in remote data centres. Read about "eventual consistency" if you are interested. This makes it practically impossible to delete data reliably. You can never be sure whether or not "ghost" copies remain after you delete data. For example on machines that failed and went offline between the write and the delete. You can expect that such machines "eventually" will receive the delete command, but you cannot be sure. Especially as the system is designed to heavily prefer data redundancy. I would guess that encryption itself is a "trick" to avoid having to solve the "deletion problem".
- vidarh 14y agoMy engineer-sense says that every item of data written is at risk of being copied into places you wouldn't think to delete them from. Note that they are not saying they are not deleting the encrypted message contents too. What they are saying simply indicates that what they promise is that they delete the keys. There are practical reasons to do it this way: You only need to ensure that you delete one key per user (you keep a "current" key, that is anything up to two days old, and a previous key that you delete once it reaches two days), vs. deleting a possibly much larger amount of data entries that might also be more likely to be cached all over the place. If I were to design a system like that, I'd try to delete the contents, but assume that I'd miss something, and aim to delete the keys too. I'd probably also make at least portion of the key depend on a site-specific set of secret rolling over with time that it should be policy not to log etc. to make it even less likely that the full key would survive longer than it should.
- sbisker 14y agoAgreed that that's a good reason not to promise to delete the data. However, they don't even say they'll try to delete it, do they? Of course, "trying" is legally just a terrible way to not promise and still get sued. I get why their lawyers would want them not even mention the data itself. Still...Facebook is not exactly trusted when it comes to the privacy of just about anything. They're trying to operate a service in the grey area between what they want to do and reality, and doing so depends heavily on people's trust in their intentions. You can guess how much I trust Facebook to keep my data private right now (if not from my timeline, then from the government, etc.)
- grandpoobah 14y agoSeems somewhat silly, the idea that it's difficult for a company to not store your stuff.
- noblethrasher 14y agoDifficult because of automatic backups, archiving, and such.
- sweis 14y agoThink about availability. A large web site is going to keep replicated copies of data across many geographic locations, plus backed up in long term storage. Those data are stored in hardware that is continually coming in and out of service. It's actually very hard to say with certainty that every copy of a particular piece of data has been deleted.
- cma 14y agoWhy should it ever be written to permanent storage?
- loeg 14y agoBecause RAM is orders of magnitude more expensive than spinning rust, or even SSDs.
- cma 14y agoThese are messages that last 20 seconds, there is no time that they will be on disk and not cached to ram anyway. (edit: well I guess it is 20 seconds after it is received)
- loeg 14y agoThe messages are stored for two days. Backups for 90… And: writing to (spinning) disk takes on the order of milliseconds. 20 seconds of RAM storage time (versus milliseconds) means several orders of magnitude larger working set size, which may well be larger than you can afford…
- white_devil 14y agoYeah, far be it from Facebook to use the pictures you post to gather personal data on you.
- DanBC 14y ago> is Facebook saving these potentially embarrassing photos and videos? No. It’s deleting them. Pokes are encrypted, and Facebook deletes the encryption keys two days after they’re read so they’re unreadable. Key backups are destroyed within 90 days, making a poke completely inaccessible. Please could someone with familiarity with English / EU law say if this is legal or not?
- loxs 14y agoSee my explanation here https://news.ycombinator.com/item?id=4957817 https://news.ycombinator.com/item?id=4957817 It might or might not be legal. But because of laws of physics and mathematics it's impossible for them to do it any other way.
- 001sky 14y agoBut because of laws of physics and mathematics... -- you mean cost/benefit. Nothing is impossible, if one is willing to pay the price.
- rmc 14y agoI'm confused by your question. How is this not legal? Most of Facebook's EU legal troubles are to do with them storing too much information for too long, in breech of EU data protection law This "deleting personal information" seems to fall within the spirit if the law
- michaelhoffman 14y agoWouldn't it be trivial for the recipient to take a screenshot of the private content and therefore retain access to it for years later?
- sandis 14y agoApp hides the content as soon as you try to take a screenshot and it notifies the sender of your attempt.
- Devilboy 14y agoLike any DRM this is easily defeated. I could run the app in a virtual machine and take the screenshot from the hypervisor or host machine instead. Or I can capture the network traffic. Or I can take a photo of my phone. And so on and so on.
- dotmanish 14y agoThe "take a photo of my phone" is the one that non-geeks can easily remember to do. And they will.
- jlgreco 14y agoAnd I imagine on any phone with a face-facing camera (would that be "forward facing", or "rear facing"?) doing that with another application and a portable makeup mirror should be trivial. All you need is an application that takes a picture without altering what is on the screen when you press both volume buttons, or something. Maybe even just takes a picture once a second for the next 30 seconds? You could make an application explicitly for this purpose, and even build in the mirrored image logic. Only one person needs to do it, then every non-technical user can use it.
- cmelbye 14y agoUgh, seriously? DRM? Come on, it's a fun app for friends to send embarrassing pictures of themselves to each other. Obviously there's an "analog hole", but this isn't for incredibly confidential photos.
- deleted 14y ago[deleted]
- rayiner 14y agoWhat is Facebook's monetization strategy for a feature that will be used primarily for 15 year olds sending each other naked pics? I can't believe they don't have one.
- captainobv 14y agoI don't get the commotion. In light of the analog hole [1], isn't this whole thing with Poke's privacy/encryption just a big pointless media/PR circus? Unless I misunderstand something here, the other party can store your data indefinitely, and no amount of DRM lockdown can really change that. [1] http://en.wikipedia.org/wiki/Analog_hole http://en.wikipedia.org/wiki/Analog_hole
- mooneater 14y agoAnd we believe them... why?
- recursive 14y agoAm I using the same facebook? For me, pokes don't seem to contain any information other than who sent them, who the target is, and when it was sent. I know I've seen pokes older than two days. They stick around for months.
- audeyisaacs 14y agoFacebook has launched a new image chat service also called Poke. It confuses me too. "The Poke app for iPhone is a simple and fun way to say hello to your friends. You can send pokes, along with messages, photos and videos, to a friend or multiple friends at once. When you send messages, photos and videos, you can choose how long they'll be available for your friends to view up to 10 seconds. After that, they disappear from the app." http://www.facebook.com/help/397568030328686/ http://www.facebook.com/help/397568030328686/