registration of [X|I]* keys beforehand

[stef]

in the file https://github.com/Inria-Prosecco/noise-star/blob/main/noise-all/api-XK/XK_25519_ChaChaPoly_BLAKE2b/XK.h#L149 the the following comment is found:

/* ...
 * we don't accept unknown remote static keys: all remote keys should have been
   registered in the device by adding the proper peers.

However the XK pattern itself is actually meant in the case the responder does not know the static key of the initiator.
By naively changing the example for KK in the examples directory. The example fails with Error: Receive message 2, since i do not register alice with bob:

    // Register Alice
    //peer *peer_alice = Noise_XK_device_add_peer(bob_device, (uint8_t*) "Alice", alice_spub);
    //if (!peer_alice) return 1;
    //peer_id alice_id = Noise_XK_peer_get_id(peer_alice);

(the example does succeed if i uncomment these lines though)

i have two questions in this regard,

1. is it possible to use noise-star in XK setting without actually knowing the initiators keys in advance?
2. is it possible to extract the public key of the initiator in the first message so that i can "register" it at that point, and possibly use it for other authorization checks later?

[stef]

ok, i guess if i change my perspective and squint i can see this as a kind of "authorized_keys" file like in ssh, this actually makes sense for "[I|X]" patterns in some use-cases. and if i do so, i also know how to ask your fine code to give me the rs of the initiator.

you can close this issue, but also keep it open as a reminder for others that are initially confused by this.