[curves] Second day NIST workshop notes

[Ron Garret]

On Jun 12, 2015, at 12:08 PM, Michael Hamburg <mike at shiftleft.org> wrote:

> Would be nice if new curves support a=-3.  Would be even nicer if prime order.  Would be nice if sqrt(b) doesn’t exist.  Unfortunately with curve25519, sqrt(b) does exist in short Weierstrass form and a=-3 not possible.

Can you please elaborate on this a bit?  Why is it desirable if sqrt(b) doesn’t exist, and to set a=-3?

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