International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Benjamin Smith

Publications

Year
Venue
Title
2021
TCHES
CTIDH: faster constant-time CSIDH 📺
This paper introduces a new key space for CSIDH and a new algorithm for constant-time evaluation of the CSIDH group action. The key space is not useful with previous algorithms, and the algorithm is not useful with previous key spaces, but combining the new key space with the new algorithm produces speed records for constant-time CSIDH. For example, for CSIDH-512 with a 256-bit key space, the best previous constant-time results used 789000 multiplications and more than 200 million Skylake cycles; this paper uses 438006 multiplications and 125.53 million cycles.
2018
ASIACRYPT
Towards Practical Key Exchange from Ordinary Isogeny Graphs
Luca De Feo Jean Kieffer Benjamin Smith
We revisit the ordinary isogeny-graph based cryptosystems of Couveignes and Rostovtsev–Stolbunov, long dismissed as impractical. We give algorithmic improvements that accelerate key exchange in this framework, and explore the problem of generating suitable system parameters for contemporary pre- and post-quantum security that take advantage of these new algorithms. We also prove the session-key security of this key exchange in the Canetti–Krawczyk model, and the IND-CPA security of the related public-key encryption scheme, under reasonable assumptions on the hardness of computing isogeny walks. Our systems admit efficient key-validation techniques that yield CCA-secure encryption, thus providing an important step towards efficient post-quantum non-interactive key exchange (NIKE).
2017
ASIACRYPT
2016
CHES
2016
JOFC
2014
EUROCRYPT
2013
ASIACRYPT
2011
ASIACRYPT
2009
JOFC
2008
EUROCRYPT