Strength of 1Password master password vs 2fac

Hi 1P folks ~

I appreciated thedean‘s recent post about password complexity requirements and this got me thinking more deeply about how complex my 1Password master password needs to be.

I use a hardware key for 2factor authentication (like a Yubikey), and I’m wondering how necessary a 70 bit+ master password is, if I use a yubikey like device too?

I suppose the attack vector there is, they steal my yubikey. The question then becomes is it just as easy for them to spend—say “only” [EDIT] $76 M, as mentioned in your article dated 2018, updated last in 2021, for a 56-bits of entropy password–to crack my password if they have possession of my yubikey like device? Or does having to use my yubikey—even though they have possession—make a [EDITs made to bits of entropy] 56 bit+ password much more expensive? I like the $1T cost of 70+ bits, that way only if Zuck, Musk, and Bezos agree to burn all their resources together can it be cracked. ;-)

Anyway, my question is—in short—do I need to have a 71-bits of entropy password if I’m using a yubikey-like device for 2fac, or not—if I want to maintain a $1T cost to attackers—were my yubikey to be stolen? (Iow, does having possession of my yubikey like device bring the cost to exactly what it would be if I weren’t using a hardware device, or does it somehow rate slow or otherwise inhibit the attacker and, essentially, add more bits of entropy or make it impossible(bly expensive) to attack a 56 bit password?)