Allow Databases secured with Challenge-Response only

[DrFlamingoo]

Hi all,
I set up a Yubikey to work without a password with the keepass database file, by simply not defining a master password but adding a Challenge-Response (yubikey). So this is a "one factor security based on a thing you have", missing the usual "thing that you know" for an actual two-factor verification scheme.
This works fine using webdav sync across several windows hosts, but it is not available as an option in keepass2android. I'd be very happy if an unlocking mechanisem based on Challenge-Response only was included.
Thanks a lot!

[PhilippC]

can't you use an empty string as password?

[DrFlamingoo]

I had not tried that so far, as I assumed that it would not be allowed during initial generation of the database file.
Thanks for your help!

[DrFlamingoo]

So, it turns out I can use an empty string in the generation of the password file using KeePass2 (as you suggested), but the android app 'keepass2android' only allows empty strings for "Password + Challenge Response for Keepass XC", not for the "Password + Challenge Response" option that I am using. If I try using the latter option, I can't select the decryption button in order to advance to the next screen.

So it would be great to either allow empty strings for this option as well, or offer a "Challenge Response" option.