Many cryptographic schemes have been established based on the hardness of lattice problems. For the asymptotic efficiency, ideal lattices in the ring of cyclotomic integers are suggested to be used in most such schemes. On the other hand in computational algebraic number theory one of the main problem is called principle ideal problem (PIP). Its goal is to find a generators of any principle ide...

We call a module  essentially retractable if HomR for all essential submodules N of M. For a right FBN ring R, it is shown that: (i)  A non-zero module  is retractable (in the sense that HomR for all non-zero ) if and only if certain factor modules of M are essentially retractable nonsingular modules over R modulo their annihilators. (ii)  A non-zero module  is essentially retractable if and on...

We study exponentiability of homomorphisms in varieties of universal algebras close to classical ones. After describing an “almost folklore” general result, we present a purely algebraic proof of “étale implies exponentiable”, alternative to the topologically motivated proof given in one of our previous papers, in a different context. We prove that only isomorphisms are exponentiable homomorphi...

Garg, Gentry and Halevi (GGH) described the first candidate multilinear maps using ideal lattices. However, Hu and Jia presented an efficient attack on GGH map, which breaks the GGH-based applications of multipartite key exchange (MPKE) and witness encryption (WE) based on the hardness of 3-exact cover problem. We describe a new construction of multilinear map using random matrix, which support...

In CRYPTO 2010, Aguilar et al. proposed a somewhat homomorphic encryption scheme, i.e. an encryption scheme allowing to compute a limited amount of sums and products over encrypted data, with a security reduction from LWE over general lattices. General lattices (as opposed to ideal lattices) do not have an inherent multiplicative structure but, using a tensorial product, Aguilar et al. managed ...