Re: Qauntum Computers and brute forcing encryption

From: Gelo Ilzi (geloilzi_at_hotmail.com)
Date: 10/28/03 

Date: Tue, 28 Oct 2003 21:30:01 +0200

> Hi,
>
> When will quantum computers be able to practically brute force a
> blowfish 256bit key?

probably never. Quantum computers can do nothing with block ciphers. More
exactly
they achive square root speedup (by Grover algorithm), i.e., complexity of
breaking
of 256 bits key will be O(2^128) which is still too much.

> I keep reading Quantum Computers are here and being used, and then
> read a recent article saying it will be at least 10 years before they
> are practical.

Currently quantum computers are still in cradle. As far I known the largest
quantum computer has only 7 bits of memory. It is based on NMR technology,
and absolutely unscaleable.

> Does anyone have any links or info on this specific subject which
> clarifies this?

There is a nice paper about this issue written by a "father" of quantum
computing:
Why Haven't More Quantum Algorithms Been Found? Journal of the ACM (JACM)
archive
Volume 50 , Issue 1 (January 2003).

All the best.

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