Haifa University - Dept. of CS Theory Seminar
Speaker : Alon Rosen, IDC.
Title: "Chosen Ciphertext Security via Correlated Products".
Date: Thursday, June 19.
Place: Haifa U. Education Building, room 570.
Time: 12:15 - 13:30
In this talk I will present a new notion of security, called one-wayness
under correlated products. The question we are interested in is what are
necessary and sufficient conditions for a function f and a distribution on
inputs (x1,...,xk), so that the function (f(x1),...,f(xk)) is one-way. The main
motivation of this study is the construction of public-key encryption schemes
that are secure against chosen-ciphertext attacks (CCA). We show that any
collection of injective trapdoor functions that is secure under very natural
correlated products can be used to construct a CCA-secure public-key encryption
scheme. The construction is simple, black-box, and admits a direct proof of
We provide evidence that security under correlated products is achievable by demonstrating that any collection of lossy trapdoor functions, a powerful primitive introduced by Peikert and Waters (STOC '08), yields a collection of injective trapdoor functions that is secure under the above mentioned natural correlated products. Although we eventually base security under correlated products on lossy trapdoor functions, we argue that the former notion is potentially weaker as a general assumption. Specifically, there is no fully-black-box construction of loss trapdoor functions from trapdoor functions that are secure under correlated products.
Based on joint work with Gil Segev.