## Cryptology ePrint Archive: Report 2011/427

A new attack on the KMOVcryptosystem

Abderrahmane Nitaj

Abstract: In this paper, we analyze the security of the KMOV public key cryptosystem. KMOV is based on elliptic curves over the ring $\mathbb{Z}_n$ where $n=pq$ is the product of two large unknown primes of equal bit-size. We consider KMOV with a public key $(n,e)$ where the exponent $e$ satisfies an equation $ex-(p+1)(q+1)y=z$, with unknown parameters $x$, $y$, $z$. Using Diophantine approximations and lattice reduction techniques, we show that KMOV is insecure when $x$, $y$, $z$ are suitably small.

Category / Keywords: public-key cryptography / KMOV, elliptic curve cryptosystem, RSA