Paper 2021/1630 Original: eprint.iacr.org/2021/1630 ↗

Exponential Increment of RSA Attack Range via Lattice Based Cryptanalysis

Abstract

The RSA cryptosystem comprises of two important features that are needed for encryption process known as the public parameter $e$ and the modulus $N$. In 1999, a cryptanalysis on RSA which was described by Boneh and Durfee focused on the key equation $ed-k\phi(N)=1$ and $e$ of the same magnitude to $N$. Their method was applicable for the case of $d<N^{0.292}$ via Coppersmith’s technique. In 2012, Kumar et al. presented an improved Boneh-Durfee attack using the same equation which is valid for any e with arbitrary size. In this paper, we present an exponential increment of the two former attacks using the variant equation $ea-\phi(N)b=c$. The new attack breaks the RSA system when $a$ and $|c|$ are suitably small integers. Moreover, the new attack shows that the Boneh-Durfee attack and the attack of Kumar et al. can be derived using a single attack. We also showed that our bound manage to improve the bounds of Ariffin et al. and Bunder and Tonien.