New hashing algorithm?

[stratacast]

I see this is using SHA1. Any plans for allowing SHA256 or SHA512 also?

[ChristophWurst]

I have no idea 🙈 @LukasReschke what do you think?

[My1]

well considerin OTP generates just 6 numbers anyway, there is probably no problem with SHA1
also newer sha versions probably arent supported by most of the TOTP apps.

[ChristophWurst]

no activity and I have no plans to work on this ATM -> close

[My1]

also other hasing algos would totally break compatibility with many apps which only do sha1

[Freeedim]

Hi guys,

I come from the future (2022), and things have changed a bit.

SHA-1 has been cracked and there are now quite some TOTP apps allowing to select another hashing algorithm.

I would suggest to keep SHA-1 as the default algorithm for compatibility purpose and to offer the user a kind of "advanced settings" option unveiling a drop-down list (or something alike) with other algorithms (SHA-256, SHA-512, SHA-2, ChaCha...).

What do you think?

[My1]

SHA-1 has been cracked and there are now quite some TOTP apps allowing to select another hashing algorithm.

are you referring to https://shattered.it?
back then it was said HMAC wasnt affected.

although having options is always good.

[Freeedim]

I guess leveraging the described attack needs the attacker's knowing the resulting hashing. And few actors have the computational power to conduct the attack in a timely way anyway.

So I would say HMAC is affected, but TOTP over SHA-1 is still quite safe in 99.99% of use cases at least.

Then it depends from whom you want to protect your data and account. Maybe a couple of users out of some millions want a TOTP guaranteed to be able to resist an NSA/FSB attack. And in that case, when you dropped Google, Microsoft etc. for obvious concerns, I guess you want to be reassured by an open-source, independent solution that supports recent and robust cryptography algorithms, just to be ahead rather than behind.

I am not a developer or a cryptologist, so I was picturing supporting a new algo as basically including its library and adding an 'algoType' parameter in the hashing function call, so I thought it was a quick win (even if a tiny win). Apologies if the implementation is actually cumbersome (I know, it's always more complicated than we foresee, even when we are experts).

[My1]

I think the issue is less the implementation, but rather the compatibility, as for example authy doesnt support anything besides standard 30 sec SHA1 6-digit TOTPs, and not sure if for example google authenticator supports other SHA methods.

I am honestly not sure what would be the bigger problem. that you have only 6 digits or that you have HMAC-SHA1.

[Freeedim]

Of course, to make that very clear, I don't suggest to drop SHA-1. I am just suggesting to add other algorithms as options. It could be additional digits too, by the way.

I actually use Aegis Authenticator and it seems to offer the possibility to customise algo and number of digits, which suddenly made me wish the same was possible on Nextcloud's side.

[My1]

I never assumed dropping sha1 just That if it's enabled that the guidance texts might need to change

[Freeedim]

Oh, yes, I see! Definitely! That's why I suggested to keep SHA-1 as the default and hide the other algorithms (and possibly the number of digits and validity time) under a deterring "advanced settings" thing...