8 ms·

This article mentions an important fact about forward secrecy: >Perfect forward secrecy is useless, it's important to note, if users don't delete their message

• xiaomai 6y ago
  I think not having it disappear by default is reasonable. My biggest complaint about signal is how hard it is to preserve history (backing up / transferring to new devices). I think the normal expectation is that your data is not going to automatically disappear unless you ask it to.
  • asquabventured 6y ago
    When was the last time you moved devices? I was able to wirelessly import my entire years old messaging and contact database when I switched iOS devices ~10 months ago. I don't recall if it used NFC, Bluetooth or having to be connected to the same WiFi network but it worked impressively well at the time.
    • xiaomai 6y ago
      one thing i have done recently that definitely didn't work is syncing history from phone->desktop. i haven't gone phone->phone in at least a couple years though--good to hear that that's working better.
      • bilal4hmed 6y ago
        They recently improved it on iOS https://signal.org/blog/ios-device-transfer/ https://signal.org/blog/ios-device-transfer/ on Android you have to do it manually and its by no means easy or intuitive if you are an everyday user. Whatsapp nails this experience on Android with the back up and transfer capability
        • Mediterraneo10 6y ago
          > Whatsapp nails this experience on Android with the back up and transfer capability Note that Whatsapp’s backups are in plaintext and sent to a Google property, while Signal’s backups (even if more cumbersome to set up) are encrypted with a key that only you know.
          • bilal4hmed 6y ago
            yes good catch, I forgot to mention that. I wanted to highlight that for the average user being able to backup and move messages to a new device easily is a big plus even if its insecure. I hope in 2021 Signal can improve their new transfer method by allowing transfers between Android devices or even ( albeit far more difficult) android and ios
        • fidelramos 6y ago
          But WhatsApp backups are stored unencrypted on Google Drive. So either you have backups or you keep your privacy from Google and Facebook.
    • jaywalk 6y ago
      The iOS transfer process uses the same technology as AirDrop, what Apple calls Multipeer Connectivity: https://developer.apple.com/documentation/multipeerconnectivity https://developer.apple.com/documentation/multipeerconnectiv... The phones create their own ad-hoc Wi-Fi network, similar to Wi-Fi Direct.
    • climb_stealth 6y ago
      I think the problem is losing access to a phone. For example because it gets dropped or stolen. The lack of good message backups on iOS makes me hesitant to recommend Signal more.
      • Mediterraneo10 6y ago
        At least on Signal for Android, you can make all the periodic backups of your Signal messages that you want: just be sure to copy the most recent backup file from your phone to another computer, and keep the encryption key (i.e. the sequence of numbers that Signal generates for you) written down somewhere. Then, if your phone does get dropped or stolen, you will have only lost messages since your last backup.
        • pseudalopex 6y ago
          Signal for iOS goes out of its way to prevent this.
        • izacus 6y ago
          The Android backups are also to SD card only - you "just" need to manually handle cron jobs to copy off device, "just" make sure you copy of a really long key (you're not allowed to enter yourself) and "just" hope that a year down the road you still find all of those data. It's a horribly shitty user experience all but most mindful techies. The issue with Signal is that their developers fundamentally don't value the content of conversations in the way that millions of other people do - people send photos of their loved ones, have meaningful conversations and they fundamentally care about not losing them. Signal developers think that that's all worthless and needs to be destroyed ASAP.
  • neckardt 6y ago
    I have the opposite problem where I can't turn disappearing messages on by default. Every time I create a new conversation I have to manually set messages to disappear after a week which I often forget to do.
  • glitchc 6y ago
    I never understand this logic. You want end-to-end encryption, which entails building a complex, clever mousetrap so that only the device in your hands is capable of viewing the messages you receive, AND you want to back them up so that they can be retrieved later on a different device that was not part of the trusted setup?? If the backup is a priority, perhaps end-to-end encryption is not suited to your use case. And no, it's not simple at all to provide this technology in a meaningful way that is both as secure as you need and as convenient as you want. Nor should it be free if it ever exists.
    • pseudalopex 6y ago
      The Android and desktop versions already do this. Why shouldn't it be free?
      • glitchc 6y ago
        Do they? Where are the encryption keys stored? Are you able to recover your backups if you lose your desktop?
        • pseudalopex 6y ago
          Desktop stores the key on disk already. Android shows a key you write down.
    • AnonC 6y ago
      Your viewpoint leaves out a larger number of people who want security (as recommended by experts) and convenience without having to understand all the nuances or complexities involved in a solution. Such a description also makes it very hard to recommend Signal to lay people because they don’t know or care much about security but do want convenience. If Signal is meant to be for a small echo chamber group to use, this is fine. If not, the convenience aspect cannot, and should not, be ignored to increase adoption.
  • bonestamp2 6y ago
    I agree with both of you. It should be off by default, but it should notify users initially and periodically about the benefits of turning it on so they are aware of it.
  • godelski 6y ago
    As someone that doesn't fret with the saving history part I'm curious why people save their texts and back them up. Honestly it is a bit creepy to me. I can understand saving special texts (especially for a short time period) but it seems weird to me that people want to save texts from a year ago that talk about what I had for breakfast. There's something I'm not getting here, can someone enlighten me? Like I've never searched my texts for something that is more than a few weeks old. Any further back than that and I just directly ask the person (it is way faster).
    • im3w1l 6y ago
      People drift apart or even die.
    • mikem170 6y ago
      One reason may be that some people are hoarders. It's in our genes, like squirrels packing away nuts for the winter. Another may be that texts are like emails for some people, and some people have reason to save important emails. I know a real estate agent that does a ton of stuff via text. I delete texts after I process them. If I get a pic I want to keep I save it and back it up on the computer. I don't really save emails, either (I empty my trash every couple of months) EDIT: added email comparison
      • godelski 6y ago
        I'm not sure the email comparison is good. We usually do a lot of business via email. So it makes sense to have records. Whereas texting we are just casually having conversations. Most people don't use it for business, though I'm sure some do. I do completely understand archiving specific texts (sorry if this wasn't clear in my original statement), but the mass saving is weird to me. It feels akin to having a conversation with my friend and them just pulling out a microphone and recording our conversation. And then when asking why the answer is "for my records" or "it's my data". And I'm accused of being the weird one. I guess I just fundamentally don't understand.
    • pseudalopex 6y ago
      Saving history doesn't have to mean saving every message.
• jolux 6y ago
  As far as I know, you still get some benefit even with it off; it means that MITM attacks are much less valuable.
• jooize 6y ago
  I tried arguing for being able to delete messages from all parties of a conversation. [1] They were feature-averse back in 2014 for good reasons, but perhaps now they would consider implementing Delete Messages When Requested on a per-conversation basis. [1] https://github.com/signalapp/Signal-Android/issues/1764 https://github.com/signalapp/Signal-Android/issues/1764 (2014)
  • godelski 6y ago
    I've participated in some form conversations on the topic. At least people on the form are very against message deleting. Although Signal does have a bidirectional "delete for everyone" feature now. But you can only do it within 3 hours of sending the message.
    • AnonC 6y ago
      Three hours is a very short duration, IMO. In my opinion, it should be at least a day (24 hours) or cover more than one’s average sleep duration so that any messages sent in haste can be removed once better senses prevail. Considering time zone variances across the people involved in chats, I think something more than 12 hours would be good. We all have a need to amend our messages after ruminating on them for sometime. The three hour limit doesn’t gel well with how humans work (on this matter, even the HN edit limit duration is very short).
      • godelski 6y ago
        Yeah so I'd encourage you to write that on the signal forums. The discussions are very one sided. The arguments against deleting are "it's my device, so my data." The people there are very unhappy with the fact that you can even delete now (feature is like 2 months old).
        • JoshTriplett 6y ago
          That argument alone should suffice. Down that path lies trying to lock down other people's devices, people complaining that they deleted a message but others have screenshots, etc. Once you've sent a message, the message is sent. Once it's on my device, it's mine. If you don't want someone to have a message, don't send it.
• tzs 6y ago
  I thought that the purpose of perfect forward secrecy was to protect against eavesdroppers who had recorded your encrypted traffic in the case of your secret keys somehow leaking. Protecting messages at rest at the source or destination is out of scope for perfect forward secrecy.
  • schoen 6y ago
    Yes, for example your key could be stolen through electromagnetic eavesdropping (Cryptography Research had an amazing demo of a practical side-channel attack at the RSA conference one time), but that doesn't mean that all of your message contents are exposed that way. Or, malware on your phone could exfiltrate your key but not all of your messages because that would somehow be more suspicious/noticeable, like if you were on a metered mobile data connection. But if the attacker is a government or has otherwise compromised telco infrastructure, the attacker might already have copies of your old encrypted traffic -- which, without forward secrecy, it could use. I think the context of the claim in the article is pretty much only for the "government physically seizes your phone and examines its contents" scenario: but even for that scenario, a user might choose to selectively delete specific messages without deleting all of them (e.g. Signal allows you to delete an entire "conversation" with a specific person). So in this threat model, either way, we also need to look into whether Signal successfully overwrites the content and metadata of the messages it deletes on the mobile device storage, because the government attacker would use forensic tools to try to undelete that data. I don't know the answer to that.
    • ghthor 6y ago
      SSD storage makes it pretty much impossible to overwrite data on the disk from the OS. Because writing is all handled internally and is copy on write you cant just write to disk sectors. The internal firmware will route the write to different parts of the disk.
      • schoen 6y ago
        I've been aware of that in the past, but it slipped my mind when I was asking this question. (So thanks.) Has anyone investigated the wear leveling of mobile device storage to see how bad/tractable this situation is at the moment?
• albntomat0 6y ago
  Auto-deleting messages by default seems like a clear violation of "the principle of least astonishment/surprise," with no clear way of designing around it. My personal view is that such a tradeoff comes down to the threat model of the individual user, and they should not be surprised by auto-deleting messages by default.
  • lmm 6y ago
    For an email-like system you expect to keep all messages forever. For a messenger-like system it's not particularly surprising if your messages expire after a fairly long period (e.g. 30 days or 180 days), IMO. E.g. I genuinely don't know (or care) whether my WhatsApp history is available or not past a month or two back.
    • godelski 6y ago
      I mean a lot of us grew up when you could only save 500 text messages. AIM didn't originally preserve things either. I'm seriously curious why people want to save everything. It seems odd to me, and honestly a bit creepy. But maybe there is a use case I don't understand.
      • deleted 6y ago
        [deleted]
    • JoshTriplett 6y ago
      People suggest, often, that Signal is the usable successor to encrypted email. If it loses data by default, it isn't a viable replacement.
• thaumasiotes 6y ago
  > The user has to somehow know that they have to do this to get the benefit of forward secrecy. I mean, this is basically true of every feature in every product.
• tmp538394722 6y ago
  Yes, it’s good to periodically delete your old content, but calling it “useless” is a stretch. Consider the context in which Signal came of age - post Snowden mass surveillance. Signal has always prioritized fighting mass surveillance. Getting individual devices hacked to recover its content is already outside of what I’d consider “mass surveillance”. That is, even if you don’t use disappearing messages, you’re much less likely to have your conversations slurped up into some PRISM aggregator type machine by using an e2e communication channel like Signal, in part due to its forward secrecy capabilities. That said - no harm in fighting targeted surveillance as well. Wether it be from a 3 letter agency, a phone thief, or an overzealous personal relationship.