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i just did the math on the power cost of a quantum computer breaking one bitcoin address:

13 days, 49 million dollars, if you did this in the USA based on 16 cents per kWH, based on having a machine with 1 million qbits.

the threat is very overblown. assuming this machine exists (which it likely won't for another 10 years), you would only break even on a UTXO of 440.4 bitcoin, at the current price per bitcoin price per kilowatt ratio. presumably building the machine itself is going to cost around the same price, as well, so that raises the minimum to cracking a UTXO of 880.8 bitcoin.

i'm sure there is work being done to find a way to allow post quantum work with as neat small keys as ECDSA and EC-schnorr (probably we could cope with 512 bits considering the cost of data storage in 10 years).

but currently also, quantum resistant public keys and signatures are like RSA/DSA, 1-4kb in length, 4-16x the amount of data currently used for a bitcoin spend signature.

nostr:nevent1qvzqqqqqqypzqnyqqft6tz9g9pyaqjvp0s4a4tvcfvj6gkke7mddvmj86w68uwe0qyvhwumn8ghj7un9d3shjtnwdaehw6r9wfjjucm0d5hszrnhwden5te0dehhxtnvdakz7qpqjc7y7vze67zzxlqv94pz73nnt093ajrwm7xz9gqpcjuftze0c98s78qw9j

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ᴛʜᴇ ᴅᴇᴀᴛʜ ᴏꜰ ᴍʟᴇᴋᴜ 4mo ago

there is a post quantum signature algorithm VDOO which requires only 96 bytes per signature. this isn't such a big deal. worst case bitcoin block limit needs to be raised to ~8mb, and the pubkey hash function expanded to SHA256 from its current RIPEMD160.

ᴛʜᴇ ᴅᴇᴀᴛʜ ᴏꜰ ᴍʟᴇᴋᴜ 4mo ago

also, keep in mind these numbers:

the current total generation capacity (which in reality is only about 80% of this) of the USA is 1.3 terawatts. so, 1300 gigawatts.

if you divide the number of gigawatts (which as i pointed out you need one to run the 1 million qbit computer) by each person in the USA, you come out to 35kw per capita capacity, and individuals are using about half of that at peak draw on a 16A circuit, probably also about teh average size of a small household circuit. so one of these computers uses the same power as about 280,000 people worst case at everyone using the full 35kw of power. so the machine is also bidding up the cost of electricity to the size of a medium sized city, just for one. this would probably mean the effect on power prices would be to nearly double them, and people would be screaming about it.