Tid: 2025-06-12 09:15 till 13:00
Plats: E:1406
Kontakt: vu.nguyen@eit.lth.se

Zoom link.

Link to Thesis in LU Research Portal.

We analyze several lightweight code-based cryptosystems in the first three works, ranging from stream ciphers to wPRFs and authentication protocols. We investigate the design weaknesses that allow us to launch attacks using various techniques. In particular, we analyze a novel LPN-based stream cipher called Firekite, a wPRFs construction, and an HB-like authentication protocol named LCMQ. Using diverse techniques in conjunction with information-set decoding algorithms (ISD), our studies improve previous results (if any) and impose stronger security parameters for said constructions. Then, we draw connections between lattice-solving algorithms and traditional syndrome decoding algorithms with our new proposal: a sieving-style ISD algorithm. Our algorithm offers a novel time-memory trade-off in solving relevant code-based parameters. In the low error-weight regime, the sieving-style ISD can use memory more efficiently without losing its competitiveness in computational performance. Thus, we introduce a valuable and practical alternative to cryptanalysis. The last two papers look at the novel RSDP problem from a new perspective - the Oracle model, analogous to the LWE or LPN problems. We construct an HB-like authentication protocol, replacing the LPN problem with the (Oracle)
RSDP problem, showing its remarkable adaptiveness to the most secure designs. In practice, RSDP structures allow incredibly efficient operations, rivaling those of LPN. Moreover, RSDP also achieves high-security guarantees with modest parameters, yielding significant superiority regarding communication cost. Finally, we expand the cryptanalysis of the RSDP problem, especially when many RSDP samples are allowed with a BKW-style solver. We analyze the concrete complexity of RSDP in new regimes outside of CROSS parameters. Hence, our work is a useful calibrating tool for similar RSDP-based cryptosystems in the future.