Paper 2014/839

A Simple and Improved Algorithm for Integer Factorization with Implicit Hints

Koji Nuida, Naoto Itakura, and Kaoru Kurosawa


Given two integers $N_1 = p_1q_1$ and $N_2 = p_2q_2$ with $\alpha$-bit primes $q_1,q_2$, suppose that the $t$ least significant bits of $p_1$ and $p_2$ are equal. May and Ritzenhofen (PKC 2009) developed a factoring algorithm for $N_1,N_2$ when $t \geq 2\alpha + 3$; Kurosawa and Ueda (IWSEC 2013) improved the bound to $t \geq 2\alpha + 1$. In this paper, we propose a polynomial-time algorithm in a parameter $\kappa$, with an improved bound $t = 2\alpha - O(\log \kappa)$; it is the first non-constant improvement of the bound. Both the construction and the proof of our algorithm are very simple; the worst-case complexity of our algorithm is evaluated by an easy argument, without any heuristic assumptions. We also give some computer experimental results showing the efficiency of our algorithm for concrete parameters, and discuss potential applications of our result to security evaluations of existing factoring-based primitives.

Available format(s)
Public-key cryptography
Publication info
Preprint. MINOR revision.
Contact author(s)
k nuida @ aist go jp
2014-10-20: received
Short URL
Creative Commons Attribution


      author = {Koji Nuida and Naoto Itakura and Kaoru Kurosawa},
      title = {A Simple and Improved Algorithm for Integer Factorization with Implicit Hints},
      howpublished = {Cryptology ePrint Archive, Paper 2014/839},
      year = {2014},
      note = {\url{}},
      url = {}
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