this post was submitted on 15 Apr 2024
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Privacy
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That would surprise me. What's your source for this?
https://signal.org/blog/secure-value-recovery/
master_key is never stored or sent to the SGX, only c2, the entropy bits. The user's password is still required to generate the key.
Brute forcing 4-6 digit pins is trivial.
And even if the user set a actual password, it's still very trivial
https://blog.cryptographyengineering.com/2020/07/10/a-few-thoughts-about-signals-secure-value-recovery/
"Very trivial" if they set a proper password? Yet the source you provide says it's robustly secure
I can't find the phrase robustly secure in the last link:
https://blog.cryptographyengineering.com/2020/07/10/a-few-thoughts-about-signals-secure-value-recovery/
Signal asks users to set a pin/password which needs to be periodically reentered. This discourages people from using high entropy passwords like BIP38.
The password is literally a pin
If you set a small pin, perhaps. Most people set a password
Pin is the suggested option, so I really doubt "most" of the people choose password
Most people who care* I guess would be more apt
For the people who really care, they can disable The pin. I believe the client will generate a BIP 38 password randomly, and use that for the data encrypted in the SVR. But all the data is still uploaded to the cloud. So if there's a problem with the SVR encoding, the BIP 38 password generation etc the data is still exploited
Not only do you have to care, everyone you talk to has to do the same thing, because if your counterparty has their key in the cloud, the conversation is at risk.
Regardless, the master key is never uploaded
All the bits to reconstruct the master key minus the pin code are uploaded. So it's equivalent to uploading to the cloud The master key itself.
Very few people are using BIP 38 level passwords. So the vast majority of people have their key constructively uploaded fully in the cloud
So my takeaways from this link and other critiques has been:
1.Signal doesn't upload your messages anywhere, but things like your contacts (e.g. people you know the usernane/identifier, but not phone number of) can get backed up online
2. You can disable this backup and fully avert this issue. (You'll lose registration lock if you do this.)
3. Short PINs should be considered breakable, and if you're on this subreddit you should probably use a relatively long password like BIP39 or some similar randomly assigned mnemonic.
4. SGX should probably also be considered breakable, although this does appear to be an effort to prevent data from leaking.
One nit to pick, messages have to transit through the signal network. And they could be recorded during transit. Carnivore style
True, but that's more or less out of the scope of this thread. I could go on for way longer about centralized versus federated services...