I wouldn’t necessarily say fantasy. Grover’s only requires 2n qubits to brute force, where n is # of bits mod N.
So consider RSA 2048 / AES 128. Still common. You’re probably in range of wifi that uses it. That would only require ~4096 qbs to brute force. For reference, Osprey (2022) had 400+ qbs and Condor (2023) has 1k+ (with ECC it’s lower but can’t remember how much).
Probably within a decade you can rent a machine with enough for these older protocols, and that’s not a very long time to hold onto data if it’s potentially high value. So “fantasy” might be a stretch.
I wouldn’t necessarily say fantasy. Grover’s only requires 2n qubits to brute force, where n is # of bits mod N.
So consider RSA 2048 / AES 128. Still common. You’re probably in range of wifi that uses it. That would only require ~4096 qbs to brute force. For reference, Osprey (2022) had 400+ qbs and Condor (2023) has 1k+ (with ECC it’s lower but can’t remember how much).
Probably within a decade you can rent a machine with enough for these older protocols, and that’s not a very long time to hold onto data if it’s potentially high value. So “fantasy” might be a stretch.