With a bad choice like SHA256, a 7 word passphrase could be cracked in as little as a few months with a single ASIC. The US government probably has a bunch of them already, so I think that an 8 word passphrase is already within reach for current tech.

Of course, with a real key derivation function like Argon2id, things would look much better.

Especially since in general the likeliest failure mode would be the user forgetting the password to their millions of dollars worth of Bitcoin keys, followed by someone attacking the password.

how long are we talking?

With SHA-256 it takes about $21 to crack a 6 character password.

$1500 to crack 7 characters.

$108,330 to crack 8 characters.

$7.8 million to crack 9 characters.

$561 million to crack 10 characters.

$40 billion to crack 11 characters.

$3 trillion to crack 12 characters.

$200 trillion to crack 13 characters.

Edit Note: BTC is kinda expensive per hash right now. Usually this would all be cheaper. Past 14 characters it could be 1 cent and still outrun the usual US budget for a couple years.

But you can refer to https://hashcat.net/hashcat/

https://www.eff.org/files/2016/07/18/eff_large_wordlist.txt

There's selection bias going on because only dumb criminals get caught, so you only hear about the dumb opsec practices of those criminals. Conversely, you'll never hear about the opsec practices of that professional crew with perfect opsec that hacked an exchange/difi contract and disappeared into thin air.

I haven't studied criminology, but I alternatively suppose someone who does that just doesn't think that far ahead. This likely also explains why the vast majority of people with these capabilities choose to live a life in accordance to their country's laws.

Or, the TLA involved have some sort of crack or acceleration procedure; the TLA say "the criminals were dumb" because the people involved can't combat that without admitting guilt, and who'd believe them. The real reason is the TLA used illegal access and tools that we wouldn't be happy they're using against the civilian population? Oh, and the people using the tools are guilty by association so they're inhibited from whistleblowing.

"Approximate Crack Time: 61,103,576,810,655,170 centuries"

Yeah, sure:)

With the Feds involved, that would be sufficient to crack the data.