[cryptography] Point compression prior art?

James A. Donald jamesd at echeque.com
Tue May 17 21:52:19 EDT 2011


Gives us the algorithm published in 1992

For elliptic curves expressed as

y^2+ y.x = x^3 + a.x^2 + b

For a given value of x, there are two possible values of y/x, differing 
by 1.

Thus, to compress the point, represent it by the full value of x, and 
the least significant bit of y/x

Analogously for elliptic curves expressed as y^2 = x^3 + a.x^2 + b.

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