We propose a Las Vegas probabilistic algorithm to compute the zeta function of a
genus-3
hyperelliptic curve defined over a finite field
Fq, with explicit real
multiplication by an order
Z[η]
in a totally real cubic field. Our main result states that this algorithm requires an expected number of
˜O((logq)6) bit-operations, where
the constant in the
˜O()
depends on the ring
Z[η]
and on the degrees of polynomials representing the endomorphism
η.
As a proof-of-concept, we compute the zeta function of a curve
defined over a 64-bit prime field, with explicit real multiplication by
Z[2cos(2π∕7)].
Keywords
point-counting, hyperelliptic curves, Schoof's algorithm,
real multiplication