Dimensions of Copeland-Erdos Sequences

The base-$k$ {\em Copeland-Erd\"os sequence} given by an infinite set $A$ of positive integers is the infinite sequence \CE_k(A) formed by concatenating the base-$k$ representations of the elements of $A$ in numerical order. This paper concerns the following four quantities. The {\em finite-state dimension} \dimfs (\CE_k(A)), a finite-state version of classical Hausdorff dimension introduced in 2001. The {\em finite-state strong dimension} \Dimfs(\CE_k(A)), a finite-state version of classical packing dimension introduced in 2004. This is a dual of \dimfs(\CE_k(A)) satisfying \Dimfs(\CE_k(A)) \geq \dimfs(\CE_k(A)). The {\em zeta-dimension} \Dimzeta(A), a kind of discrete fractal dimension discovered many times over the past few decades. The {\em lower zeta-dimension} \dimzeta(A), a dual of \Dimzeta(A) satisfying \dimzeta(A)\leq \Dimzeta(A). We prove the following. \dimfs(\CE_k(A))\geq \dimzeta(A). This extends the 1946 proof by Copeland and Erd\"os that the sequence \CE_k(\mathrm{PRIMES}) is Borel normal. \Dimfs(\CE_k(A))\geq \Dimzeta(A). These bounds are tight in the strong sense that these four quantities can have (simultaneously) any four values in $[0,1]$ satisfying the four above-mentioned inequalities.Comment: 19 page

WinLomac: Low Water Mark integrity protection for Windows 2000

Computer security has long been one of the most important research areas in computer science. In recent years, the rapid growth in Internet based industry has raised the importance of computer security to an unprecedented level. However, at the same time, profit driven commercial software development always leaves security concerns behind the quick incorporation of new functionalities. Therefore, the need to improve the security of these products is very urgent now. Microsoft Windows 2000, as one of the most popular operating systems, also needs to be improved. Especially, because of the unavailability of the necessary documentation and source code, few third party research and development have been done for Windows 2000 operating system kernel. In this paper, we introduce WinLomac, a prototype security enhancement software for Windows 2000 operating system that enforces Low Water Mark integrity model based Mandatory Access Control in the kernel

Dimensions of Copeland-Erdos Sequences

The base-k Copeland-Erdös sequence given by an infinite set A of positive integers is the infinite sequence CEk(A) formed by concatenating the base-k representations of the elements of A in numerical order. This paper concerns the following four quantities. • The finite-state dimension dimFS(CEk(A)), a finite-state version of classical Hausdorff dimension introduced in 2001. • The finite-state strong dimension DimFS(CEk(A)), a finite-state version of classical packing dimension introduced in 2004. This is a dual of dimFS(CEk(A)) satisfying DimFS(CEk(A)) ≥ dimFS(CEk(A)). • The zeta-dimension Dimζ(A), a kind of discrete fractal dimension discovered many times over the past few decades. • The lower zeta-dimension dimζ(A), a dual of Dimζ(A) satisfying dimζ(A) ≤ Dimζ(A). We prove the following. 1. dimFS(CEk(A)) ≥ dimζ(A). This extends the 1946 proof by Copeland and Erdös that the sequence CEk(PRIMES) is Borel normal. 2. DimFS(CEk(A)) ≥ Dimζ(A). 3. These bounds are tight in the strong sense that these four quantities can have (simultane-ously) any four values in [0, 1] satisfying the four above-mentioned inequalities

Curves That Must Be Retraced

We exhibit a polynomial time computable plane curve ${bf Gamma}$ that has finite length, does not intersect itself, and is smooth except at one endpoint, but has the following property. For every computable parametrization $f$ of ${bfGamma}$ and every positive integer $m$, there is some positive-length subcurve of ${bfGamma}$ that $f$ retraces at least $m$ times. In contrast, every computable curve of finite length that does not intersect itself has a constant-speed (hence non-retracing) parametrization that is computable relative to the halting problem