In modern cryptography, structured lattices from ring-based LWE and NTRUNTRU are useful to construct efficient and compact cryptosystems. Search problems of ring-based LWE and NTRU can be reduced to particular cases of the shortest vector problemShortest vector problem (SVP) on Kannan’s embedding and the NTRU lattices, respectively. In this paper, we expand Kannan’s embedding and the NTRU lattices for solving the ring-based LWE and the NTRU problems, respectively. Both expanded lattices include many short vectors that are amplified by using rotations of secret short vectors. Since many target short vectors are embedded in our expanded lattices, it could increase the success probability for solving the ring-based LWE and the NTRU problems by using the block Korkine–Zolotarev (BKZ) reduction algorithm. We demonstrate by experiments the efficacy of our expansions from viewpoints of the success probability and the running time.

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Expanded Lattices for Solving Ring-Based LWE and NTRU Problems

  • Satoshi Nakamura,
  • Masaya Yasuda

摘要

In modern cryptography, structured lattices from ring-based LWE and NTRUNTRU are useful to construct efficient and compact cryptosystems. Search problems of ring-based LWE and NTRU can be reduced to particular cases of the shortest vector problemShortest vector problem (SVP) on Kannan’s embedding and the NTRU lattices, respectively. In this paper, we expand Kannan’s embedding and the NTRU lattices for solving the ring-based LWE and the NTRU problems, respectively. Both expanded lattices include many short vectors that are amplified by using rotations of secret short vectors. Since many target short vectors are embedded in our expanded lattices, it could increase the success probability for solving the ring-based LWE and the NTRU problems by using the block Korkine–Zolotarev (BKZ) reduction algorithm. We demonstrate by experiments the efficacy of our expansions from viewpoints of the success probability and the running time.