On ideal and subalgebra coefficients in a class k-algebras

Let k be a commutative field with prime field $k0$ and A a k- algebra. Moreover, assume that there is a k-vector space basis $ω$ of A that satisfies the following condition: for all $ω1, ω2 ∈ ω$ ,the product $ω1ω2$ is contained in the $k0$-vector space spanned by $ω$. It is proven that the concept of minimal field of definition from polynomial rings and semigroup algebras can be generalized to the above class of (not necessarily associative) k-algebras. Namely, let U be a one-sided ideal in A or a k-subalgebra of A. Then there exists a smallest $k' ≤ k$ with U-as one-sided ideal resp. as k-algebra—being generated by elements in the $k'$-vector space spanned by $ω$

Pitfalls in public key cryptosystems based on free partially commutative monoids and groups

At INDOCRYPT 2003 Abisha, Thomas, and Subramanian proposed two public key schemes based on word problems in free partially commutative monoids and groups. We show that both proposals are vulnerable to chosen ciphertext attacks, and thus in the present form must be considered as insecure.This work has been partially supported by the German Academic Exchange Service DAAD and the Spanish M.E.C. as part of the BaSe CoAT project within the Acciones Integradas Hispano-Alemanas

08491 Executive Summary -- Theoretical Foundations of Practical Information Security

Designing, building, and operating secure information processing systems is a complex task, and the only scientific way to address the diverse challenges arising throughout the life-cycle of security criticial systems is to consolidate and increase the knowledge of the theoretical foundations of practical security problems. To this aim, the mutual exchange of ideas across individual security research communities can be extraordinary beneficial. Accordingly, the motivation of this Dagstuhl seminar was the integration of different research areas with the common goal of providing an integral theoretical basis that is needed for the design of secure information processing systems

08491 Abstracts Collection -- Theoretical Foundations of Practical Information Security

From 30.11. to 05.12.2008, the Dagstuhl Seminar 08491 ``Theoretical Foundations of Practical Information Security \u27\u27 was held in Schloss Dagstuhl~--~Leibniz Center for Informatics. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

A short comment on the affine parts of SFLASH^{v3}

In [http://eprint.iacr.org/2003/211/] SFLASH^{v3} is presented, which supersedes SFLASH^{v2}, one of the digital signature schemes in the NESSIE Portfolio of recommended cryptographic primitives. We show that a known attack against the affine parts of SFLASH^{v1} and SFLASH^{v2} carries over immediately to the new version SFLASH^{v3}: The 861 bit representing the affine parts of the secret key can easily be derived from the public key alone