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Signal Secure Backups

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Re: Signal Secure Backups

#391

Post by traceroute66 »

sneak wrote: post #265
joshjob42 wrote: post #98

Earlier quoted context omitted.

They do and have done for years now. There’s been a files app since 2017. They’ve had Advanced Data Protection available for iOS backups since 2022. Signal has just been lazy and found maintaining the Android backups to be a pain, so they refused to implement it for iOS.

ADP is off by default (this is why iMessage isn’t really e2ee), and importantly, isn’t available in all countries . I believe in the UK you are legally barred from having access to iCloud ADP.

> I believe in the UK you are legally barred from having access to iCloud ADP.

Apple are still busy fighting the UK government on it in closed-court.

Apple-bashers can continue their hate, but give Apple their due:

    1. they are going in all guns blazing fighting the UK government instead of rolling over
    2. if they succeed, I think they well-deserve the credit.

Re: Signal Secure Backups

#392

Post by daveoc64 »

styanax wrote: post #387
daveoc64 wrote: post #264

Earlier quoted context omitted.

The existing backup feature on Android doesn't do an incremental backup. I just ran a backup, and it was 850MB. So having my phone upload something of that size every day would be a bit annoying. Most of the major cloud storage platforms don't offer sync on Android. It's not really a good fit for how the filesystem is used by Android apps. I currently only do a Signal backup every few months (when I remember), and ma…

> I just ran a backup, and it was 850MB. So having my phone upload something of that size every day would be a bit annoying It may be inconvenient but this can be solved by using the features in the app to review your storage and save those thousands of images/audio/file sequestered inside the app out to the filesystem, then delete them from the app. You're not backing up "chats" you're backing up your image library…

Reducing the size of the backup would solve one problem, but it's really the lack of automation of the process that's the annoying part.

Re: Signal Secure Backups

#393

Post by Y-bar »

palata wrote: post #371
Y-bar wrote: post #344

Earlier quoted context omitted.

They are somewhat correct though, Signal has written code explicitly to prevent iOS users from including Signal data in Apple’s encrypted local and/or cloud backups. Allowing encrypted backups was free for Signal, but they spent time and money to prevent it for iOS users. Part of the code the wrote to prevent backups in question: https://github.com/signalapp/Signal-iOS/blob/5590f09c3643f12...

It would be interesting to have Signal's justification for that, but I can totally imagine that it is a security feature. As in: they may not want their users to inadvertently share their Signal messages with Apple.

Lot's of people have requested justification in related Github issues there, but Signal has not given a clear answer. If there was a security problem with the encryption process I believe a CVE or similar would have been in order because it would affect millions of users.

Re: Signal Secure Backups

#394

Post by internet_points »

prism56 wrote: post #188

Finally installed signal. I have 220 phone contacts and 1 had it installed. Uphill battle here. WhatsApp and imessage are so prevalent in the UK

Meanwhile in Norway, of 520 phone contacts (of which many are things like cabs, restaurants, realtor from way back when) – 83 are on signal. And it's not like I have particularly privacy-conscious friends, that I know of.

Re: Signal Secure Backups

#395

Post by upofadown »

The key is 64 characters? Even if that key is made out of decimal digits that works out to 212 bits. That seems quite excessive for a symmetrical key you are hoping to have a user deal with directly. It appears that the usability of this scheme could be significantly improved by simply using a shorter key.

Re: Signal Secure Backups

#396

Post by _aavaa_ »

crtasm wrote: post #302
_aavaa_ wrote: post #151

Earlier quoted context omitted.

A backup option has been missing for years. Future plans on this particular topic seem to take forever.

It's been backing up to my SD card for years, I've not set up a script to transfer it off-device though.

That only works on android. The same basic functionally, even backing up to a place on the phone, has been missing.

Re: Signal Secure Backups

#397

Post by _aavaa_ »

jimkleiber wrote: post #355
_aavaa_ wrote: post #151

Earlier quoted context omitted.

A backup option has been missing for years. Future plans on this particular topic seem to take forever.

I built a micro-journaling app back in the day and wanted it to be highly secure. Backups seemed to be one of the most vulnerable surfaces for that. I imagine their delay might have been a combination of a technological and ideological worries, as that's what I experienced.

How did you encrypt the data at rest and why was that also not good for the backup?

Re: Signal Secure Backups

#398

Post by palata »

Y-bar wrote: post #393
palata wrote: post #371

Earlier quoted context omitted.

It would be interesting to have Signal's justification for that, but I can totally imagine that it is a security feature. As in: they may not want their users to inadvertently share their Signal messages with Apple.

Lot's of people have requested justification in related Github issues there, but Signal has not given a clear answer. If there was a security problem with the encryption process I believe a CVE or similar would have been in order because it would affect millions of users.

I was not talking about a security flaw.

I was saying that maybe, Signal did not want to push their users to trust the Apple backup by default.

Signal is a nonprofit foundation, it's not like they are trying to squeeze their users with their own secure backup.

Re: Signal Secure Backups

#399

Post by growse »

upofadown wrote: post #395

The key is 64 characters? Even if that key is made out of decimal digits that works out to 212 bits. That seems quite excessive for a symmetrical key you are hoping to have a user deal with directly. It appears that the usability of this scheme could be significantly improved by simply using a shorter key.

What's the specific use case that benefits from a shorter key?

The only interaction I can ever see having with this key is putting it into and taking it out of my password manager....

Re: Signal Secure Backups

#400

Post by greysonp »

codethief wrote: post #267
greysonp wrote: post #59

Earlier quoted context omitted.

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…

Hi Greyson! > But this new thing is all cross-platform, and in the near future we'll even be making our local backups cross-platform. This is excellent news! Will there also be official documentation on the backup format, potentially even official tooling like signalbackup-tools[0] to access/parse backups offline? I'm asking because, having used Signal/TextSecure for 10 years now, my backups are worth a lot to me (ob…

Hi! I don't know if we'll have anything super official, but the code is obviously all open source, and the backup file is just a stream of protobufs[1], so it shouldn't be too bad to make a tool. I know have some rough CLI tools sitting around -- I'll see if there's anything we want to clean up and release publicly when the local backup portion of this launches.

Also, as someone else noted, the format is indeed incremental. So while we'll still do the thing where we keep the last two backups on disk, because those two backups will share almost all the same media files, the size on disk will be much much smaller. As someone with a 50 GB backup file, this was very much a goal for me :)

[1] https://github.com/signalapp/Signal-Android/blob/main/app/sr...

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