This is a tale of the intersection between thermal physics, cosmology, and a tiny amount of computer science to answer a seemingly innocuous question: “How strong does a password need to be for it to be physically impossible to brute-force, ever?”

• A password with 256 bits of entropy is practically immune to brute-force attacks large enough to quite literally burn the world, but is quite trivial to crack with a universe-scale fuel source.
• A password with 327 bits of entropy is nearly impossible to crack even if you burn the whole observable universe trying to do so.

See also https://sr.ht/~seirdy/MOAC/