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Signal Secure Backups

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Re: Signal Secure Backups

#281

Post by codethief »

wpollock wrote: post #68
chimeracoder wrote: post #21

Earlier quoted context omitted.

> It would be really useful to have more client-side control over media storage. That way, I could better manage storage growth without wiping entire threads. > For example, being able to see all media across chats, sort by file size, and optionally group by conversation would make it much easier to clean things up. I have good news for you: this already exists. On Android: Settings >> Data and Storage >> Manage Stor…

On my Samsung: Settings >> Device Care >> Storage

I think you're talking about Android settings, though, not Signal settings?

Re: Signal Secure Backups

#282

Post by bsimpson »

ngrilly wrote: post #125

What is the reason for saving the end-to-end encrypted backup files on Signal backup servers instead of iCloud or Google backup service, as most of us are already paying for this storage?

The "Signal should exist" part of me is happy to donate $2/mo to help them keep the lights on, but I really did expect that to be an option alongside Drive/Dropbox/et al, not the only option.

Re: Signal Secure Backups

#283

Post by codethief »

hiq wrote: post #175
chimeracoder wrote: post #40

Earlier quoted context omitted.

> I do that and then sync that folder with another computer using SyncThing. AFAIK SyncThing only monitors for changes between files with matching names, and Signal stores each backup with a separate (timestamped) filename. Are you storing every day's backup individually, or do you have some tool for deduplicating?

Encrypted backups can't be deduplicated unless the encryption is flawed. There shouldn't be a way to tell that one Signal backup is somewhat related to another, unless you have the passphrase. That also means that Syncthing can't do better than sending the full backup. But if you're syncing via wifi (e.g. at home) it's not really a problem anyway.

> Encrypted backups can't be deduplicated unless the encryption is flawed.

Would you mind elaborating on why this would be an issue? 1) Tools like borgbackup provide the exact functionality you're describing and considered secure. 2) Encrypted file systems also don't re-encrypt your entire HDD whenever you change a single file.

Re: Signal Secure Backups

#284

Post by drnick1 »

john01dav wrote: post #231
drnick1 wrote: post #154

Earlier quoted context omitted.

Signal is open source, so security claims can be verified unlike anything made by Apple or other Big Tech companies.

What does this have to do with the message that you replied to?

I meant to reply to another comment.

Re: Signal Secure Backups

#285

Post by codethief »

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 splitting things up into same-sized chunks, like e.g. borgbackup does.)

> At the core of secure backups is a 64-character recovery key that is generated on your device. This key is yours and yours alone; it is never shared with Signal’s servers. This key is different from your Signal PIN, which serves different purposes.

Both recovery key and Signal PIN seem to serve the exact same purpose, though, namely restoring data (conversations, contacts, account, …)? Why not unify them?

Re: Signal Secure Backups

#286

Post by EGreg »

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.

Re: Signal Secure Backups

#287

Post by highwind »

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.

Re: Signal Secure Backups

#288

Post by elvisloops »

joshjob42 wrote: post #100
elvisloops wrote: post #60

Earlier quoted context omitted.

This post says disappearing messages are included in the backups. You have to enable disappearing messages with a timer of less than 24 hours to ensure that you can opt out.

Sure but the backup happens each day and then gets overwritten/deleted when the next days backup happens (which then deletes the disappearing messages that are expiring express the next backup). It just ensures you have access to any messages that you’re supposed to have access to according to the timers on said messages.

That's not how forward secrecy works. Ciphertext isn't "deleted" unless the key used to encrypt it is also deleted. That's the point of Signal's cutting edge protocol. This undoes all of that.

Re: Signal Secure Backups

#289

Post by tymscar »

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.

Most likely they have different keys for absolutely no other reason than the fact that they were bought/made separately. I honestly would prefer to have a single key to my building.

Re: Signal Secure Backups

#290

Post by elvisloops »

evbogue wrote: post #155
krior wrote: post #123

Earlier quoted context omitted.

afaik the key material is regenerated for every message. new keys can be derived for every subsequent message you send, but only until you get a reply, then a new key exchange takes place. And the key material for message m1 cannot derive keys for the messages that came before m1. If the old key material gets properly deleted then there is only a very small window of compromise. backing up those keys would defeat the…

yes, agreed, and isn't this feature re-encrypting all of the material without a ratchet or asymmetrical boxing?

Yes, it undoes all of the security features of Signal's encryption protocol.
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