  For the integer $ D=pq$ of the product of two distinct odd primes, we
construct an elliptic curve $E_{2rD}:y^2=x^3-2rDx$ over $\mathbb Q$, where $r$
is a parameter dependent on the classes of $p$ and $q$ modulo 8, and show,
under the parity conjecture, that the elliptic curve has rank one and
$v_p(x([k]Q))\not=v_q(x([k]Q))$ for odd $k$ and a generator $Q$ of the free
part of $E_{2rD}(\mathbb Q)$. Thus we can recover $p$ and $q$ from the data $D$
and $ x([k]Q))$. Furthermore, under the Generalized Riemann hypothesis, we
prove that one can take $r<c\log^4D$ such that the elliptic curve $E_{2rD}$ has
these properties, where $c$ is an absolute constant.
