The COLDCARD attacker isn’t bruteforcing your passphrase

I think everyone is missing the economics of this attack.

The attacker isn’t trying to brute-force your passphrase.

They’re generating vulnerable seeds as fast as possible and checking whether those seeds control any bitcoin.

The moment you add a BIP-39 passphrase, every candidate seed now requires deriving and checking an additional wallet. Even a passphrase that would only take an hour to brute-force in isolation completely destroys the attacker’s throughput when applied across millions or billions of candidate seeds.

Realistically, they’ll check no passphrase, and maybe a tiny list of extremely common ones. Anything beyond that makes the attack economically unattractive.

That’s why I suspect the overwhelming majority of victims will turn out to be users who didn’t use a BIP-39 passphrase at all.