Key recycling in authentication

In their seminal work on authentication, Wegman and Carter propose that to authenticate multiple messages, it is sufficient to reuse the same hash function as long as each tag is encrypted with a one-time pad. They argue that because the one-time pad is perfectly hiding, the hash function used remains completely unknown to the adversary. Since their proof is not composable, we revisit it using a composable security framework. It turns out that the above argument is insufficient: if the adversary learns whether a corrupted message was accepted or rejected, information about the hash function is leaked, and after a bounded finite amount of rounds it is completely known. We show however that this leak is very small: Wegman and Carter's protocol is still $\epsilon$-secure, if $\epsilon$-almost strongly universal$_2$ hash functions are used. This implies that the secret key corresponding to the choice of hash function can be reused in the next round of authentication without any additional error than this $\epsilon$. We also show that if the players have a mild form of synchronization, namely that the receiver knows when a message should be received, the key can be recycled for any arbitrary task, not only new rounds of authentication.Comment: 17+3 pages. 11 figures. v3: Rewritten with AC instead of UC. Extended the main result to both synchronous and asynchronous networks. Matches published version up to layout and updated references. v2: updated introduction and reference

Cryptographic security of quantum key distribution

This work is intended as an introduction to cryptographic security and a motivation for the widely used Quantum Key Distribution (QKD) security definition. We review the notion of security necessary for a protocol to be usable in a larger cryptographic context, i.e., for it to remain secure when composed with other secure protocols. We then derive the corresponding security criterion for QKD. We provide several examples of QKD composed in sequence and parallel with different cryptographic schemes to illustrate how the error of a composed protocol is the sum of the errors of the individual protocols. We also discuss the operational interpretations of the distance metric used to quantify these errors.Comment: 31+23 pages. 28 figures. Comments and questions welcom

Minimal Assumption Derivation of a weak Clauser-Horne Inequality

According to Bell's theorem a large class of hidden-variable models obeying Bell's notion of local causality conflict with the predictions of quantum mechanics. Recently, a Bell-type theorem has been proven using a weaker notion of local causality, yet assuming the existence of perfectly correlated event types. Here we present a similar Bell-type theorem without this latter assumption. The derived inequality differs from the Clauser-Horne inequality by some small correction terms, which render it less constraining.Comment: 25 pages, 3 figure

Pathologic analysis of liver transplantation for primary biliary cirrhosis

A retrospective histopathologic review of all pathologic specimens from 394 adult liver transplant patients was undertaken with clinical correlation to determine if primary biliary cirrhosis has affected the posttrans‐plant course compared to all other indications for liver transplantation and if recurrent primary biliary cirrhosis has occurred after liver transplantation. We also compared the histopathologic features seen in native livers with primary biliary cirrhosis to failed allografts with chronic rejection. One hundred six of the 394 adult patients transplanted during this time (1981 to July, 1986) fulfilled clinicopathologic criteria for a diagnosis of primary biliary cirrhosis. Neither the incidence nor any qualitative pathologic feature of histologically documented acute cellular rejection differentiated subjects transplanted for primary biliary cirrhosis vs. other diseases. No correlation between the titers of antimitochon‐drial antibody and the presence of posttransplant hepatic dysfunction based on liver enzyme profiles or the development of chronic rejection was seen in patients transplanted for primary biliary cirrhosis. Minor differences noted in the posttransplant course of primary biliary cirrhosis patients as compared to other conditions (higher incidence of chronic rejection as a cause of graft failure) was seen, but this did not significantly affect graft or patient survival. Recurrent primary biliary cirrhosis could not be diagnosed with certainty in any patient. A comparison of failed chronically rejected allografts vs. native hepatectomies obtained from patients with primary biliary cirrhosis revealed the presence of chronic obliterative vasculopathy, centrilobular cholestasis, and lack of granulomas, cirrhosis, cholan‐giolar proliferation, copper‐associated protein deposition and Mallory's hyalin in specimens with chronic rejection. In contrast, livers removed from patients with primary biliary cirrhosis demonstrated a mild vasculopathy, cirrhosis, granulomas, copper‐associated protein deposition, Mallory's hyalin and periportal cholestasis. Both conditions demonstrated a nonsuppurative destructive cholangitis with bile duct paucity. Copyright © 1988 American Association for the Study of Liver Disease

Minimal assumption derivation of a Bell-type inequality

John Bell showed that a big class of local hidden-variable models stands in conflict with quantum mechanics and experiment. Recently, there were suggestions that empirical adequate hidden-variable models might exist, which presuppose a weaker notion of local causality. We will show that a Bell-type inequality can be derived also from these weaker assumptions.Comment: 8 pages, 6 figures; assumption 8 revised, typos correcte

SCOR: Software-defined Constrained Optimal Routing Platform for SDN

A Software-defined Constrained Optimal Routing (SCOR) platform is introduced as a Northbound interface in SDN architecture. It is based on constraint programming techniques and is implemented in MiniZinc modelling language. Using constraint programming techniques in this Northbound interface has created an efficient tool for implementing complex Quality of Service routing applications in a few lines of code. The code includes only the problem statement and the solution is found by a general solver program. A routing framework is introduced based on SDN's architecture model which uses SCOR as its Northbound interface and an upper layer of applications implemented in SCOR. Performance of a few implemented routing applications are evaluated in different network topologies, network sizes and various number of concurrent flows.Comment: 19 pages, 11 figures, 11 algorithms, 3 table

A Linear Control Theory Analysis of Transverse Coherent Bunch Instabilities Feedback Systems (The Control Theory Approach to Hill's Equation)

There is an on-going effort to build a feedback system for transverse coherent bunch instabilities for ALS [1,2,3]. The beam dynamics issues were already addressed in the conceptual design report [ 4] and more detailed studies have been earned out [5]. On-going work is the development of a general simulation code including the full 6-dirnensional dynamics for coherent bunch instabilities (by using Taylor series maps) as well as related feedback systems [6]. Recently, there has been some confusion about how to choose the gain matrix in the feedback loop. In particular, the current analytical formulas were found (from numerical simulations by D. Briggs using the newly developed simulation code) to only be valid if ak = 0 at the kicker. This motivated us to perform a more careful design study of the transverse feedback system based on linear control theory. This paper presents the general formulas for tuning the system. Also, by a careful analytical study of the performance of the system, based on linear accelerator theory combined with linear control theory for sampled systems, we discovered that the performance of the system can be dramatically improved by slightly changing one of the two coefficients in the gain matrix

Advances and visions in large-scale hydrological modelling : proceedings of the 11th Workshop on Large-scale Hydrological Modelling ; preface

In 1998 the German Universities of Kassel and Giessen organised a workshop on water and solute transport in large drainage basins. The workshop focused on analysing and summarising the state of research, existing problems and perspectives in this research area. It was the second of a series of annual workshops since 1997 that became an important discussion forum for the German-speaking research community in the field of hydrological modelling. Now the 11th Workshop on Large-scale Hydrological Modelling referred to the same questions as posed in 1998 in order to evaluate the developments and advances of the last ten years. Based on keynote presentations, the workshop focused on discussion in working groups where also posters were presented. This volume of "Advances in Geosciences" comprises seven papers referring to the poster contributions. At the end of the volume, an overview paper summarises the outcome of the workshop presentations and discussions (Doll et al.). ..