phoenix@ugcs.caltech.edu on Tue, 24 Dec 1996 Wrote:
>Apart from the possible difficulty of making a kilobit
>quantum computer, I hadn't heard that they would be useful
>for cracking symmetric ciphers. They could factor numbers
>happily, thus bye-bye RSA and Blum-Blum-Shup; can they do
>tons of IDEA or RC4 attempts as well?
If a Quantum Computers is ever made then the only Cryptography that would
still work would be one time pads and Quantum Cryptography. One time pads
were used in the first world war, but they are very hard to implement because
it's difficult to distribute pads securely to everyone who needs one. Quantum
Cryptography has already been used in the real world and not just in the lab,
the only reason it isn't more popular is that we already have public key
cryptography and nobody yet has a Quantum Computers. I should add that if a
Quantum Computer is made then the world will change so fast and so radically
that the fact that you can no longer use PGP safely would be the last thing
you'd be worrying about.
John K Clark johnkc@well.com
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