A Weil pairing on the $p$-torsion of ordinary elliptic curves over the dual numbers of $K$

Abstract

For an elliptic curve $E$ over any field $K$, the Weil pairing $e_n$ is a bilinear map on $n$-torsion. For $K$ of characteristic $p>0$, the map $e_n$ is degenerate if and only if $n$ is divisible by $p$. In this paper, we consider $E$ over the dual numbers $K[\epsilon]$ and define a non-degenerate ``Weil pairing on $p$-torsion" which shares many of the same properties of the Weil pairing. We also show that the discrete logarithm attacks on $p$-torsion subgroups of Semaev and R\"uck may be viewed as Weil-pairing-based attacks, just like the MOV attack. Finally, we describe an attack on the discrete logarithm problem on anomalous curves, analogous to that of Smart, using a lift of $E$ over the dual numbers of the finite field of $p$ elements.