Results 1  10
of
42
Revocation and Tracing Schemes for Stateless Receivers
, 2001
"... Abstract. We deal with the problem of a center sending a message to a group of users such that some subset of the users is considered revoked and should not be able to obtain the content of the message. We concentrate on the stateless receiver case, where the users do not (necessarily) update their ..."
Abstract

Cited by 173 (4 self)
 Add to MetaCart
Abstract. We deal with the problem of a center sending a message to a group of users such that some subset of the users is considered revoked and should not be able to obtain the content of the message. We concentrate on the stateless receiver case, where the users do not (necessarily) update their state from session to session. We present a framework called the SubsetCover framework, which abstracts a variety of revocation schemes including some previously known ones. We provide sufficient conditions that guarantees the security of a revocation algorithm in this class. We describe two explicit SubsetCover revocation algorithms; these algorithms are very flexible and work for any number of revoked users. The schemes require storage at the receiver of log N and 1 2 log2 N keys respectively (N is the total number of users), and in order to revoke r users the required message lengths are of r log N and 2r keys respectively. We also provide a general traitor tracing mechanism that can be integrated with any SubsetCover revocation scheme that satisfies a “bifurcation property”. This mechanism does not need an a priori bound on the number of traitors and does not expand the message length by much compared to the revocation of the same set of traitors. The main improvements of these methods over previously suggested methods, when adopted to the stateless scenario, are: (1) reducing the message length to O(r) regardless of the coalition size while maintaining a single decryption at the user’s end (2) provide a seamless integration between the revocation and tracing so that the tracing mechanisms does not require any change to the revocation algorithm.
Generalized binary search
 In Proceedings of the 46th Allerton Conference on Communications, Control, and Computing
, 2008
"... This paper addresses the problem of noisy Generalized Binary Search (GBS). GBS is a wellknown greedy algorithm for determining a binaryvalued hypothesis through a sequence of strategically selected queries. At each step, a query is selected that most evenly splits the hypotheses under consideratio ..."
Abstract

Cited by 30 (0 self)
 Add to MetaCart
This paper addresses the problem of noisy Generalized Binary Search (GBS). GBS is a wellknown greedy algorithm for determining a binaryvalued hypothesis through a sequence of strategically selected queries. At each step, a query is selected that most evenly splits the hypotheses under consideration into two disjoint subsets, a natural generalization of the idea underlying classic binary search. GBS is used in many applications, including fault testing, machine diagnostics, disease diagnosis, job scheduling, image processing, computer vision, and active learning. In most of these cases, the responses to queries can be noisy. Past work has provided a partial characterization of GBS, but existing noisetolerant versions of GBS are suboptimal in terms of query complexity. This paper presents an optimal algorithm for noisy GBS and demonstrates its application to learning multidimensional threshold functions. 1
Sorting and Searching in the Presence of Memory Faults (without Redundancy)
 Proc. 36th ACM Symposium on Theory of Computing (STOC’04
, 2004
"... We investigate the design of algorithms resilient to memory faults, i.e., algorithms that, despite the corruption of some memory values during their execution, are able to produce a correct output on the set of uncorrupted values. In this framework, we consider two fundamental problems: sorting and ..."
Abstract

Cited by 21 (4 self)
 Add to MetaCart
We investigate the design of algorithms resilient to memory faults, i.e., algorithms that, despite the corruption of some memory values during their execution, are able to produce a correct output on the set of uncorrupted values. In this framework, we consider two fundamental problems: sorting and searching. In particular, we prove that any O(n log n) comparisonbased sorting algorithm can tolerate at most O((n log n) ) memory faults. Furthermore, we present one comparisonbased sorting algorithm with optimal space and running time that is resilient to O((n log n) ) faults. We also prove polylogarithmic lower and upper bounds on faulttolerant searching.
Resilient search trees
 IN PROCEEDINGS OF 18TH ACMSIAM SODA
, 2007
"... We investigate the problem of computing in a reliable fashion in the presence of faults that may arbitrarily corrupt memory locations. In this framework, we focus on the design of resilient data structures, i.e., data structures that, despite the corruption of some memory values during their lifetim ..."
Abstract

Cited by 18 (4 self)
 Add to MetaCart
We investigate the problem of computing in a reliable fashion in the presence of faults that may arbitrarily corrupt memory locations. In this framework, we focus on the design of resilient data structures, i.e., data structures that, despite the corruption of some memory values during their lifetime, are nevertheless able to operate correctly (at least) on the set of uncorrupted values. In particular, we present resilient search trees which achieve optimal time and space bounds while tolerating up to O ( √ log n) memory faults, where n is the current number of items in the search tree. In more detail, our resilient search trees are able to insert, delete and search for a key in O(log n + δ 2) amortized time, where δ is an upper bound on the total number of faults. The space required is O(n + δ).
Reliably executing tasks in the presence of untrusted entities
 Proceedings of the 25th IEEE Symposium on Reliable Distributed Systems
, 2006
"... In this work we consider a distributed system formed by a master processor and a collection of n processors (workers) that can execute tasks; worker processors are untrusted and might act maliciously. The master assigns tasks to workers to be executed. Each task returns a binary value, and we want t ..."
Abstract

Cited by 15 (5 self)
 Add to MetaCart
In this work we consider a distributed system formed by a master processor and a collection of n processors (workers) that can execute tasks; worker processors are untrusted and might act maliciously. The master assigns tasks to workers to be executed. Each task returns a binary value, and we want the master to accept only correct values with high probability. Furthermore, we assume that the service provided by the workers is not free; for each task that a worker is assigned, the master is charged with a workunit. Therefore, considering a single task assigned to several workers, our goal is to have the master computer to accept the correct value of the task with high probability, with the smallest possible amount of work (number of workers the master assigns the task). We explore two ways of bounding the number of faulty processors: (a) we consider a fixed bound f < n/2 on the maximum number of workers that may fail, and (b) a probability p < 1/2 of any processor to be faulty (all processors are faulty with probability p, independently of the rest of processors). Our work demonstrates that it is possible to obtain high probability of correct acceptance with low work. In particular, by considering both mechanisms of bounding the number of malicious workers, we first show lower bounds on the minimum amount of (expected) work required, so that any algorithm accepts the correct value with probability of success 1 − ε, where ε ≪ 1 (e.g., 1/n). Then we develop and analyze two algorithms, each using a different decision strategy, and show that both algorithms obtain the same probability of success 1 − ε, and in doing so, they require similar upper bounds on the (expected) work. Furthermore, under certain conditions, these upper bounds are asymptotically optimal with respect to our lower bounds.
Robust polynomials and quantum algorithms
 Theory of Computing Systems
, 2005
"... We define and study the complexity of robust polynomials for Boolean functions and the related faulttolerant quantum decision trees, where input bits are perturbed by noise. We show that, in contrast to the classical model of Feige et al., every Boolean function can be computed by O(n) quantum quer ..."
Abstract

Cited by 15 (5 self)
 Add to MetaCart
We define and study the complexity of robust polynomials for Boolean functions and the related faulttolerant quantum decision trees, where input bits are perturbed by noise. We show that, in contrast to the classical model of Feige et al., every Boolean function can be computed by O(n) quantum queries even in the model with noise. This implies, for instance, the somewhat surprising result that every Boolean function has robust degree bounded by O(n). 1
The Karmed Dueling Bandits Problem
"... We study a partialinformation onlinelearning problem where actions are restricted to noisy comparisons between pairs of strategies (also known as bandits). In contrast to conventional approaches that require the absolute reward of the chosen strategy to be quantifiable and observable, our setting ..."
Abstract

Cited by 15 (6 self)
 Add to MetaCart
We study a partialinformation onlinelearning problem where actions are restricted to noisy comparisons between pairs of strategies (also known as bandits). In contrast to conventional approaches that require the absolute reward of the chosen strategy to be quantifiable and observable, our setting assumes only that (noisy) binary feedback about the relative reward of two chosen strategies is available. This type of relative feedback is particularly appropriate in applications where absolute rewards have no natural scale or are difficult to measure (e.g., userperceived quality of a set of retrieval results, taste of food, product attractiveness), but where pairwise comparisons are easy to make. We propose a novel regret formulation in this setting, as well as present an algorithm that achieves (almost) informationtheoretically optimal regret bounds (up to a constant factor). 1
Optimal resilient sorting and searching in the presence of memory faults
 IN PROC. 33RD INTERNATIONAL COLLOQUIUM ON AUTOMATA, LANGUAGES AND PROGRAMMING, VOLUME 4051 OF LECTURE NOTES IN COMPUTER SCIENCE
, 2006
"... We investigate the problem of reliable computation in the presence of faults that may arbitrarily corrupt memory locations. In this framework, we consider the problems of sorting and searching in optimal time while tolerating the largest possible number of memory faults. In particular, we design an ..."
Abstract

Cited by 14 (3 self)
 Add to MetaCart
We investigate the problem of reliable computation in the presence of faults that may arbitrarily corrupt memory locations. In this framework, we consider the problems of sorting and searching in optimal time while tolerating the largest possible number of memory faults. In particular, we design an O(n log n) time sorting algorithm that can optimally tolerate up to O ( √ n log n) memory faults. In the special case of integer sorting, we present an algorithm with linear expected running time that can tolerate O ( √ n) faults. We also present a randomized searching algorithm that can optimally tolerate up to O(log n) memory faults in O(log n) expected time, and an almost optimal deterministic searching algorithm that can tolerate O((log n) 1−ǫ) faults, for any small positive constant ǫ, in O(log n) worstcase time. All these results improve over previous bounds.
Communication Complexity and Secure Function Evaluation
, 2001
"... A secure function evaluation protocol allows two parties to jointly compute a function f(x; y) of their inputs in a manner not leaking more information than necessary. A major result in this field is: "any function f that can be computed using polynomial resources can be computed securely using ..."
Abstract

Cited by 13 (1 self)
 Add to MetaCart
A secure function evaluation protocol allows two parties to jointly compute a function f(x; y) of their inputs in a manner not leaking more information than necessary. A major result in this field is: "any function f that can be computed using polynomial resources can be computed securely using polynomial resources" (where `resources' refers to communication and computation). This result follows by a general transformation from any circuit for f to a secure protocol that evaluates f . Although the resources used by protocols resulting from this transformation are polynomial in the circuit size, they are much higher (in general) than those required for an insecure computation of f . For the design of efficient secure protocols we suggest two new methodologies, that differ with respect to their underlying computational models. In one methodology we utilize the communication complexity tree (or branching program) representation of f . We start with an efficient (insecure) protocol for f and transform it into a secure protocol. In other words, "any function f that can be computed using communication complexity c can be can be computed securely using communication complexity that is polynomial in c and a security parameter". The second methodology uses the circuit computing f , enhanced with lookup tables as its underlying computational model. It is possible to simulate any RAM machine in this model with polylogarithmic blowup. Hence it is possible to start with a computation of f on a RAM machine and transform it into a secure protocol. We show many applications of these new methodologies resulting in protocols efficient either in communication or in computation. In particular, we exemplify a protocol for the "millionaires problem", where two partici...
Robust quantum algorithms and polynomials
 CoRR
, 2003
"... We study the complexity of robust quantum algorithms. These still work with high probability if the n input bits are noisy. We exhibit a robust quantum algorithm that recovers the complete input with high probability using O(n) queries. This implies that every nbit function can be quantum computed ..."
Abstract

Cited by 12 (2 self)
 Add to MetaCart
We study the complexity of robust quantum algorithms. These still work with high probability if the n input bits are noisy. We exhibit a robust quantum algorithm that recovers the complete input with high probability using O(n) queries. This implies that every nbit function can be quantum computed robustly with O(n) queries, which contrasts with Feige et al.’s Ω(n log n) classical bound for PARITY. We also give similar bounds on the degrees of multilinear polynomials that robustly approximate Boolean functions. 1