Recovering Secrets From Prefix-Dependent Leakage

We discuss how to recover a secret bitstring given partial information obtained during a computation over that string, assuming the computation is a deterministic algorithm processing the secret bits sequentially. That abstract situation models certain types of side-channel attacks against discrete logarithm and RSA-based cryptosystems, where the adversary obtains information not on the secret exponent directly, but instead on the group or ring element that varies at each step of the exponentiation algorithm.Our main result shows that for a leakage of a single bit per iteration, under suitable statistical independence assumptions, one can recover the whole secret bitstring in polynomial time. We also discuss how to cope with imperfect leakage, extend the model to k-bit leaks, and show how our algorithm yields attacks on popular cryptosystems such as (EC)DSA.

A Static Analysis of Uplift During Strong Earthquakes of Unanchored Flat-Bottom Cylindrical Shell Tanks

For analyzing the uplift displacement of the tank bottom plate statically and precisely, this paper develops a shell element, ring element and spring element partially attached to the ring element. These elements are defined as a semi-analytical finite element. Moreover in analyzing uplift of the tank bottom plate precisely, the ring element can deal with effects of the large deformation, while the spring element enables to express the partial contact between the tank bottom plate and foundation. Dead load, hydro-pressure and inertia force due to earthquakes acceleration as well as dynamic pressure of fluid induced by bulging and rocking motions of the tank are applied statically. Comparison of results by the proposed method and that computed by the explicit FE Analysis reveals that the accurate uplift displacement is not obtained until all physical conditions involved in the tank rocking motion and the inward deformation of the tank shell is properly considered.