Am Montag, dem 19.07.2021 um 10:15 +0200 schrieb Hannes Reinecke: > On 7/18/21 2:56 PM, Stephan Müller wrote: > > Am Sonntag, 18. Juli 2021, 14:37:34 CEST schrieb Hannes Reinecke: > > > The key is also used when using the ffdhe algorithm. > > > Note: I _think_ that I need to use this key for the ffdhe algorithm, > > > because the implementation I came up with is essentially plain DH with > > > pre-defined 'p', 'q' and 'g' values. But the DH implementation also > > > requires a 'key', and for that I'm using this key here. > > > > > > It might be that I'm completely off, and don't need to use a key for our > > > DH implementation. In that case you are correct. > > > (And that's why I said I'll need a review of the FFDHE implementation). > > > But for now I'll need the key for FFDHE. > > > > Do I understand you correctly that the dhchap_key is used as the input to > > the > > DH - i.e. it is the remote public key then? It looks strange that this is > > used > > for DH but then it is changed here by hashing it together with something > > else > > to form a new dhchap_key. Maybe that is what the protocol says. But it > > sounds > > strange to me, especially when you think that dhchap_key would be, say, > > 2048 > > bits if it is truly the remote public key and then after the hashing it is > > 256 > > this dhchap_key cannot be used for FFC-DH. > > > > Or are you using the dhchap_key for two different purposes? > > > > It seems I miss something here. > > > No, not entirely. It's me who buggered it up. > I got carried away by the fact that there is a crypto_dh_encode_key() > function, and thought I need to use it here. Thank you for clarifying that. It sounds to me that there is no defined protocol (or if there, I would be wondering how the code would have worked with a different implementation). Would it make sense to first specify a protocol for authentication and have it discussed? I personally think it is a bit difficult to fully understand the protocol from the code and discuss protocol-level items based on the code. Thanks Stephan
