International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Chi-Jen Lu

Affiliation: Institute of Info. Science, Academia Sinica

Publications

Year
Venue
Title
2010
ASIACRYPT
2009
EUROCRYPT
2007
EUROCRYPT
2007
EPRINT
Secure PRNGs from Specialized Polynomial Maps over Any $F_q$
We prove that a random map drawn from any class ${\frak C}$ of polynomial maps from $F_q^n$ to $F_q^{n+r}$ that is (i) totally random in the affine terms, and (ii) has a negligible chance of being not strongly one-way, provides a secure PRNG (hence a secure stream cipher) for any q. Plausible choices for ${\frak C}$ are semi-sparse (i.e., the affine terms are truly random) systems and other systems that are easy to evaluate from a small (compared to a generic map) number of parameters. To our knowledge, there are no other positive results for provable security of specialized polynomial systems, in particular sparse ones (which are natural candidates to investigate for speed). We can build a family of provably secure stream ciphers a rough implementation of which at the same security level can be more than twice faster than an optimized QUAD (and any other provably secure stream ciphers proposed so far), and uses much less storage. This may also help build faster provably secure hashes. We also examine the effects of recent results on specialization on security, e.g., Aumasson-Meier (ICISC 2007), which precludes Merkle-Damgaard compression using polynomials systems {uniformly very sparse in every degree} from being universally collision-free. We conclude that our ideas are consistent with and complements these new results. We think that we can build secure primitives based on specialized (versus generic) polynomial maps which are more efficient.
2006
TCC
2006
JOFC
2004
JOFC
2002
ASIACRYPT
2002
CRYPTO
2001
ASIACRYPT