When the necessary conditions are not sufficient: sequences with zero autocorrelation function

Recently K. T. Arasu (personal communication) and Yoseph Strassler, in his PhD thesis, The Classification of Circulant Weighing Matrices of Weight 9, Bar-Ilan University, Ramat-Gan, 1997, have intensively studied circulant weighing matrices, or single sequences, with weight 9. They show many cases are non-existent. Here we give details of a search for two sequences with zero periodic autocorrelation and types (1,9), (1,16) and (4,9). We find some new cases but also many cases where the known necessary conditions are not sufficient. We instance a number of occasions when the known necessary conditions are not sufficient for the existence of weighing matrices and orthogonal de-signs constructed using sequences with zero autocorrelation function leading to intriguing new questions

Covert Distributed Computing Using Java Through Web Spoofing

We use the Web Spoofing attack reported by Cohen and also the Secure Internet Programming Group at Princeton University to give a new method of achieving covert distributed computing with Java. We show how Java applets that perform a distributed computation can be inserted into vulnerable Web pages. This has the added feature that users can rejoin a computation at some later date through bookmarks made while the pages previously viewed were spoofed. Few signs of anything unusual can be observed. Users need not knowingly revisit a particular Web page to be victims. We also propose a simple countermeasure against such a spoofing attack, which would be useful to help users detect the presence of Web Spoofing. Finally, we introduce the idea of browser users, as clients of Web-based services provided by third parties, paying for these services by running a distributed computation applet for a short period of time

Construction of cubic homogeneous boolean bent functions

We prove that cubic homogeneous bent functions f : V2n → GF(2) exist for all n ≥ 3 except for n = 4

On the Internal Structure of ALPHA-MAC

ALPHA-MAC is a MAC function which uses the building blocks of AES. This paper studies the internal structure of this new design. First, we provide a method to find second preimages based on the assumption that a key or an intermediate value is known. The proposed searching algorithm exploits the algebraic properties of the underlying block cipher and needs to solve eight groups of linear functions to find a second preimage. Second, we show that our idea can also be used to find internal collisions under the same assumption. We do not make any claims that those findings in any way endanger the security of this MAC function. Our contribution is showing how algebraic properties of AES can be used for analysis of this MAC function

Two complex orthogonal space-time codes for eight transmit antennas

Two new constructions of complex orthogonal space-time block codes of order 8 based on the theory of amicable orthogonal designs are presented and their performance compared with that of the standard code of order 8. These new codes are suitable for multi-modulation schemes where the performance can be sacrificed for a higher throughput

Amicable Orthogonal Designs of Order 8 for Complex Space-Time Block Codes

New amicable orthogonal designs AODs(8; 1; 1; 1; 2; 2; 2), AODs(8; 1; 1; 4; 1; 2; 2), AODs(8; 1; 2;2; 2; 2; 4), AODs(8; 1; 2; 2; 1; 2; 4), AODs(8; 1; 1; 2; 1; 2; 4), AODs(8; 1; 2; 4; 2; 2; 2), AODs(8; 1; 1; 4; 1; 1; 2; 2), AODs(8; 2; 2; 2; 2; 2; 2; 2; 2) and AODs(8; 1; 1; 1; 2; 1; 2; 2; 2) are found by applying a new theorem or by an exhaustive search. Also some previously undecided cases of amicable pairs are demonstrated to be non-existent after a complete search of the equivalence classes for orthogonal designs