Reduced Memory Meet-in-the-Middle Attack against the NTRU Private Key

NTRU is a public-key cryptosystem introduced at ANTS-III. The two most used techniques in attacking the NTRU private key are meet-in-the-middle attacks and lattice-basis reduction attacks. In the 2007 CRYPTO paper “A Hybrid Lattice-Reduction and Meet-in-the-Middle Attack Against NTRU” both techniques are combined and it is pointed out that the largest obstacle to attacks is the memory capacity that is required for the meet-in-the-middle phase. In this paper an algorithm is presented that applies low-memory techniques to find ‘golden’ collisions to Odlyzko’s meet-in-the-middle attack against the NTRU private key. Several aspects of NTRU secret keys and the algorithm are analysed. The running time of the algorithm with a maximum storage capacity of w is estimated and experimentally verified. Experiments indicate that decreasing the storage capacity by a factor c increases the running time by a factor √ c.

• Type: Journal
• Year: 2016
• Where: IACR
• Authors: Christine van Vredendaal
• Keywords: Biometrics, IACR 2016