[Cryptography] Why prefer symmetric crypto over public key crypto?

[Andrea Shepard]

On Sat, Sep 07, 2013 at 08:45:34PM -0400, Perry E. Metzger wrote:
> I'm unaware of an ECC equivalent of the Shor algorithm. Could you
> enlighten me on that?

Shor's algorithm is a Fourier transform, essentially.  It can find periods of
a function you can implement as a quantum circuit with only polynomially many
invocations.  In particular, when that function is exponentiation in a group,
it can find the orders of group elements.  This allows finding discrete
logarithms in BQP for any group in which exponentiation is in P.

-- 
Andrea Shepard
<andrea at persephoneslair.org>
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