psk-needs-presentation chronology #359
Description
The network spec reads:
If the PSK consumer wants to initiate authentication, the PSK consumer sends a auth-spake2-handshake message to the PSK presenter with the psk-status field set to psk-needs-presentation and the public-value field set to pA.
However, pA = w*M + X with w being derived from the PSK. This means that the PSK consumer, which won't have the PSK yet until it is has been presented by the presenter and subsequently entered by the user, cannot compute pA yet.
A possible alternative would be:
- consumer to presenter: Handshake(psk-needs-presentation, null)
- presenter to consumer: Handshake(psk-shown, pA) // Presumably this party would take role A in this design.
- consumer to presenter: Handshake(psk-input, pB)
I guess that would be quite similar to the NeedPsk flow we had before.