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Lemmy Support @lemmy.ml randint @lemm.ee

Google Authenticator and Twilio Authy generate different codes for Lemmy. One works, the other doesn't.

Hi. I was trying to set up 2FA in my settings, where there is a button named "2FA installation link." I right clicked on the button, copied the link, and put it into a QR code generator. I scanned it with Twilio Authy on my phone to add it. To my surprise, when I tried using it to log in, the generated codes simply do not work. I have 20ish entries on Authy and they all work, with the Lemmy accounts being the outliers. I have also tested the 2FA on my other account at feddit.nl, and it doesn't work with Authy either.

So, I tried using Google Authenticator instead. I used it to scan the very same QR code, and it spits out different codes from those generated by Authy. The ones generated by GAuthenticator work, whereas the Authy ones don't work. I wonder what the issue is?

Edit: grammar

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13 comments

  • I believe the issue is that Lemmy expects the codes to be generated using the SHA256 algorithm, while most generator apps use SHA1.

    • Ahhh, thanks! After closer inspection of the link otpauth://totp/lemm.ee:randint?secret=[redacted, 64 characters]&algorithm=SHA256&issuer=lemm.ee, it does indeed specify SHA256. Looks like Authy just uses SHA1 regardless. Maybe I should switch back to GAuthenticator, but you know, Google...

      • If twilio doesn't work but you don't want to use Google, try Aegis or Bitwarden. Both available on f-droid. For totp on Bitwarden you either need to self-host the database using vaultwarden or pay for the pro version.

      • LastPass Authenticator can use SHA256, it works for logging in to my Lemmy instance. And you can use the app independently of LastPass, keeping everything on your device.

      • There are some other authenticator apps out there, fully open source, offline, and that support sha256.

        I found Authenticator Pro to have the best ui, but many people also use andOTP because it has more features.

  • 2FA does not completely work at the moment

    • Ah, ok. Thanks!

      Edit: I just read the comment by @gnzl@nc.gnzl.cl, and apparently the root cause is that Authy uses SHA1 despite the link clearly specifying SHA256. Now I wonder what you mean by 2FA doesn't completely work yet?

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