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Signal Secure Backups

(signal.org)
988 points keyboardJones | 4 comments | 08 Sep 25 16:43 UTC | HN request time: 0.001s | source
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upofadown ◴[09 Sep 25 11:44 UTC] No.45180609[source]▶
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.
replies(1): >>45180690 #
1. growse ◴[09 Sep 25 11:54 UTC] No.45180690[source]▶
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....

replies(1): >>45180923 #
2. upofadown ◴[09 Sep 25 12:18 UTC] No.45180923[source]▶
The article specifically suggests writing the key down in a notebook. A single incorrect digit and the scheme fails much later in a way catastrophic to the user.
replies(1): >>45182643 #
3. whyever ◴[09 Sep 25 14:44 UTC] No.45182643[source]▶
Signal asks you to repeat the key immediately before even enabling backups. It cannot fail much later unless you modify the digit after the check.
replies(1): >>45183835 #
4. upofadown ◴[09 Sep 25 15:56 UTC] No.45183835{3}[source]▶
A longer key makes typing a bunch of characters back into the phone much less usable.