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Comment by greysonp | Hacker News Reader

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, random, local key). So not the most portable!

But this new thing is all cross-platform, and in the near future we'll even be making our local backups cross-platform.

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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 (obviously) and there have been times when I would have liked to mine & process my backed-up data. (Extract media from conversations in an automated manner, build a more elaborate search, …)

My backups have also reached the point where they are so big (15-20 GB) that it's starting to become difficult to conduct a backup each day and sync it successfully before it gets overridden 48h later. So unless I start using the new "cloud backup" feature[1] (which I'm not sure I want to), at some point I will have to archive my existing Signal conversations somewhere and start from scratch (i.e. reset the app). In that case, it would be nice if there was an officially documented way to merge & read new and old backups offline (on my desktop), similar to what [0] provides right now.

[0]: https://github.com/bepaald/signalbackup-tools

[1]: EDIT: Actually, it seems like the new cloud backup feature doesn't support incremental backups, either? https://news.ycombinator.com/item?id=45175387

They are indeed incremental, and smaller than the current monolithic backups that Signal currently creates. [0] Yay!

[0]: https://news.ycombinator.com/item?id=45176074

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...

> I'll see if there's anything we want to clean up and release publicly when the local backup portion of this launches.

That would be fantastic! Thanks so much!

> As someone with a 50 GB backup file, this was very much a goal for me :)

Haha, I'm glad I'm not the only one!

Hey, please get signal to release all the infrastructure automation code so someone could audit all of signal's infra and even fork if we ever needed to because of U.S. laws or so on.

There's no reason to keep it secret and no reason why signal won't speak to this point.

Thanks!

What a ridiculous request.

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.

Will the new backup format support also conversion of filetypes between Android and iOS? In the past Voice Memos from Android couldn't be opened on iOS if they weren't sent directly between participants.

That's really surprising to me.

iOS has had pretty decent audio format support for a few years now: even though you can't directly import FLAC files to iTunes/Music, they are supported in the OS itself since 2017 and play fine both in Files and in Safari. The other big mainstream formats (WAV, AIFF, MP3, AAC, and ALAC) have been supported for years, and even Opus finally got picked up in 2021.

About the only non-niche audio format that isn't supported natively on Apple platforms at this point is Vorbis, which was fully superseded by Opus well over a decade ago. Even then, I believe it's possible to get Vorbis support in iOS apps using various media libraries, although I'm sure Apple frowns upon it.

I'd really love to know what's causing that incompatibility.

The issue is OGG with Opus (for me) which was used by WhatsApp but isn't natively supported under iOS.

https://github.com/signalapp/Signal-iOS/issues/4539

Do you know roughly how long before the iOS version comes out? I want to switch to iOS from android.

Are there any plans to allow backups to a custom server or another folder?

From tfa:

> But secure backups aren’t the end of the road. The technology that underpins this initial version of secure backups will also serve as the foundation for more secure backup options in the near future. Our future plans include letting you save a secure backup archive to the location of your choosing, alongside features that let you transfer your encrypted message history between Android, iOS, and Desktop devices.

Thanks, totally overlooked that last paragraph.

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