Signal's finally getting desktop history sync!
Hello, all! Some of you are aware that we’ve been working on a pretty cool device-independent backup format, and now we’re looking to test our first use-case: syncing your message history with a newly-linked device! You heard that right – your newly-linked devices will finally have all of your messa...
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Interesting! I wonder how this works under the hood, if it's p2p.
Is this safe?
Yes! Everything is end-to-end encrypted at all times. The data sent over to your desktop is encrypted with a strong, single-use 256-bit key that only your linked device has access to. That key is sent over the same pre-existing encrypted channel where we share other crucial keys with the linked device already. Which is to say, if you feel comfortable with the way we link devices today, you can continue to feel comfortable with this new addition.
Where’s all of my older media?
As noted above, we can only sync media sent/received in the last 45 days.
What if I don’t want to sync my message history to my newly-linked device?
You don’t have to! You can choose whether or not you want to sync your messages during the linking process.
What if everything works fine?
Still post a log! They’re useful to get a sense of performance numbers, and logs could indicate non-fatal-but-still-bad things that happened during the backup/import.
Doesn't seem to be. Seems relayed via their servers.
There is also this quote, which is weird:
The only media that syncs is media that was sent/received in the last 45 days, because that’s how long encrypted media lives on Signal’s servers in order to match the current maximum timeframe for queued messages for offline devices. Media older that that will not be available.
So that begs the question, if text messages don't live longer, why are they able to sync from older than 45 days? I'm guessing its because they are sent p2p? But in that case, why is media then not also sent p2p? Is it because of amount of data/transfer speeds?
It's probably not sent P2P. It's probably sent via their server as relay. If they pushed media from the sender device to the receiver, they'd have to reupload all that which could be a lot of traffic which costs, so they just relay the media they already have and only reupload the text. That's my hypothesis.
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