Yubico Forum

Im finally got my Yubico 4C nano in my mailbox.

Im currently toying around with U2F now, and wonder:

Is there any way, I can combine a string S, and a U2F public key, so it render the string E(S), and then send it to the yubikey for signing, which should result in the string S getting sent back?
Eg, I want to transform the challenge into something the U2F key can decrypt.
So I can simply check if initially generated random string S equals entered string, access is granted.