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netsecwarrior33 karma

(I'm not OP, but...)

Quantum computers can perform large numbers of operations simultaneously.

One of the simplest ways to break encryption is through brute force. Pick an initial key, try to decrypt the message, see if the result makes sense. Try another key, and another, until all the keys have been tried. The defense against this is that encryption keys are large - usually 2128 bits or more. That means a brute force attack would require so much computing power and time, that it is impractical.

Quantum computers could theoretically try all 2128 keys at once. A bit in a classical computer and be 0 or 1. A qubit in a quantum computer can be in an uncollapsed state where it's either 0 or 1. If you have 128-qubits input, which is uncollapsed, theoretically a quantum computer can perform all 2128 operations simultaneously.

This is a bit of an over-simplification. In particular, for breaking symmetric ciphers, actual techniques won't work this well. But it is thought that the common public key algorithms (like RSA and Diffie-Helman) could be broken.

netsecwarrior5 karma

Maybe the hospitals have different rules

netsecwarrior3 karma

Yeah, as far as I know, quantum computers can break cryptography, but not computer security in general.

For symmetric ciphers, encrypting multiple times - or increasing the key length - seems to be enough. But for public key ciphers a more fundamental redesign is needed - hence there being jobs for these guys.

netsecwarrior3 karma

I know that in the UK the NHS has extensive preparations. For example, if a plane has potential issues, nearby hospitals are informed, just in case, and can defer non urgent procedures. Probably still chaos in a major incident, but they definitely try to be prepared.

netsecwarrior2 karma

It's a dupe