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Signal Secure Backups

signal.org

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Re: Signal Secure Backups

#291

Post by amatecha »

greysonp wrote: post #59
amluto wrote: post #8

Wow, maybe as a side effect users will be able to migrate between Android and iOS without losing their message history. Seriously, why is the migration protocol completely different on the two platforms?

Hi there, Signal dev here. The new backup format is indeed cross-platform. I've successfully restored backups on an iPhone, we're just stabilizing things :) If you're curious, the reason that Android's current local backups aren't cross platform is because it was made a long time ago, and it's literally a dump of all the sqlite statements that can be used to recreate Android's sqlite database (encrypted with a strong…

Will you guys ever ship an update that allows me to use my Signal iOS install that had a partially-broken migration from an older device? I was able to receive/read messages, but couldn't send. I tried to re-register but now my client is completely broken and crashes when I enter the registration verification code I get via SMS.

Re: Signal Secure Backups

#292

Post by elvisloops »

maqp wrote: post #158
elvisloops wrote: post #7

I can't believe Signal is doing this. Signal is known for its cutting-edge cryptographic protocol, but this feature has the effect of throwing that out the window and replacing it with a single static key. If a device with this enabled goes through the whole advanced protocol to receive a message (double ratcheting etc), then turns around and uploads it back to Signal’s servers with a static key, isn't that a roundab…

>Signal is known for its cutting-edge cryptographic protocol, but this feature has the effect of throwing that out the window and replacing it with a single static key The exfiltration of which is as easy as exfiltration of database on device. You're not running an IDS scanning 100% of your device LTE traffic in case that happens. >isn't that a roundabout way of replacing all of signal's protocol and its forward secr…

It's not opt in: signal protocol for a group chat is eliminated if one person in the group chat turns this on, whether or not you do. Communicating with someone who acts adversarially is different from Signal itself adding features that are adversarial.

Re: Signal Secure Backups

#293

Post by codethief »

EGreg wrote: post #286
codethief wrote: post #285

Hi @greysonp > Once you’ve enabled secure backups, your device will automatically create a fresh secure backup archive every day, replacing the previous day’s archive. So IIUC backups will not be incremental and I will have to re-upload my 15 GB backup archive every day? Why is that? What's the security risk here? (Obviously I'm not suggesting encrypting & uploading each message & media file individually but splittin…

The PIN is a lot easier to guess on a remote machine storing a backup, the space is small. In the context of your device, they can throttle it.

Ah yes, the Signal PIN is backed by Intel SGX to ensure it can't be hacked even if the user has not provided enough entropy. However, why not simply rule out the low-entropy case altogether and use that randomly generated 64-character key throughout? That way, we also wouldn't have to trust Intel SGX… (which I think we shouldn't)

Re: Signal Secure Backups

#294

Post by nimchimpsky »

highwind wrote: post #287
codethief wrote: post #285

Hi @greysonp > Once you’ve enabled secure backups, your device will automatically create a fresh secure backup archive every day, replacing the previous day’s archive. So IIUC backups will not be incremental and I will have to re-upload my 15 GB backup archive every day? Why is that? What's the security risk here? (Obviously I'm not suggesting encrypting & uploading each message & media file individually but splittin…

I'm guessing the same reason why my house's front door and back door use different keys.

[dead]

Re: Signal Secure Backups

#295

Post by prima-facie »

codethief wrote: post #285

Hi @greysonp > Once you’ve enabled secure backups, your device will automatically create a fresh secure backup archive every day, replacing the previous day’s archive. So IIUC backups will not be incremental and I will have to re-upload my 15 GB backup archive every day? Why is that? What's the security risk here? (Obviously I'm not suggesting encrypting & uploading each message & media file individually but splittin…

I'm assuming the backup format uses a container (like Veracrypt volumes), which grows in size forever, and cannot be backed up incrementally. I ran into the same issue when backing up loopback LUKS volumes. An elegant solution in this case was switching to Gocryptfs which encrypts each file individually, but then can mount the entire folder as a whole with fuse. This means only modified files need to be synchronised to the remote.

Re: Signal Secure Backups

#296

Post by elvisloops »

codethief wrote: post #285

Hi @greysonp > Once you’ve enabled secure backups, your device will automatically create a fresh secure backup archive every day, replacing the previous day’s archive. So IIUC backups will not be incremental and I will have to re-upload my 15 GB backup archive every day? Why is that? What's the security risk here? (Obviously I'm not suggesting encrypting & uploading each message & media file individually but splittin…

Giving people a 64-character key also feels uncharacteristically crude for Signal. It's not realistic to hand people 64 characters and tell them to “store this securely.” Most people will screenshot it, and those screenshots will end up in unencrypted cloud backups.

That's less of a problem when the backups are local, because access to the local backups implies access to the device, but if the backups are in the cloud with no forward secrecy, this seems like a huge security backslide for Signal.

Re: Signal Secure Backups

#297

Post by prima-facie »

I would love if they implemented a feature to prune media files larger than ~10MiB from the existing backup file. This way the file size would not grow to astronomical proportions so quickly.

Re: Signal Secure Backups

#298

Post by Silhouette »

varenc wrote: post #213
Silhouette wrote: post #202

Earlier quoted context omitted.

Note that in all cases, Signal could/should still fully encrypt this data before pushing it to the provider; the backup wouldn't be expected to be "legible" to the user. That seems like an unhelpful limitation for a lot of people. For me - and as far as I know literally everyone I communicate with using Signal - the reason to use it is the E2EE for the messages. Once we have the messages or media on our own devices w…

Agree with the sentiment, but I can understand why they don't offer this. Rational or not, people will feel less safe if all their messages can just be easily exported to plaintext. A few scenarios where this might matter like the 'evil maid attack' where someone briefly has access to your unlocked phone. But I just use this project to export my signal messages to plaintext: https://github.com/tbvdm/sigtop I have it…

Rational or not, people will feel less safe if all their messages can just be easily exported to plaintext.

IMHO the point is that it's not rational. Signal is as vulnerable to the analogue hole as any other messaging platform that displays the messages on a phone screen. There was never any credible way to prevent someone who has received your message from keeping or passing on the information it contained. The idea is as unrealistic as the "disappearing message/photo" applications when confronted with any cheap phone or camera separate to the one showing that message/photo. Ultimately if you don't trust the recipient of your information to treat it as you would wish then your only choice is not to send them the information in the first place.

Re: Signal Secure Backups

#299

Post by zbrozek »

nar001 wrote: post #237
nikeee wrote: post #212

> alongside features that let you transfer your encrypted message history between Android, iOS, and Desktop devices. That's actually the feature I've been looking forward to. As I moved vom Android to iOS, I lost _all_ message histories from all messenger apps that use E2EE (Signal, WhatsApp, Threema, etc). The only one that "just worked" was Telegram due to not being encrypted. WhatsApp had a migration app that has…

You already can, if you at least set up desktop, you can transfer also message history, though you won't have your media older than 45 days. Maybe it can work as a stopgap before they roll out encrypeted backups everywhere

That's a weird and crappy arbitrary limitation when I could move an arbitrary amount of data between the two devices otherwise. It's the worst part of Signal.

Re: Signal Secure Backups

#300

Post by UltraSane »

codethief wrote: post #274
UltraSane wrote: post #239

Earlier quoted context omitted.

USB transfer is by far the best way to transfer large amounts of data to and from phones.

Really? Ever since Android devices ceased to be regular USB storage devices and switched to MTP, this has never worked well for me. MTP is incredibly slow.

What method do you find to be faster?
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