waashk/dblp huggingface dataset:
probabilistic treatment of mixes to hamper traffic analysis. the goal of anonymity providing techniques is to preservethe privacy of users, who has communicated withwhom, for how long, and from which location, by hidingtraffic information. this is accomplished by organizing additionaltraffic to conceal particular communication relationshipsand by embedding the sender and receiver of amessage in their respective anonymity sets. if the number ofoverall participants is greater than the size of the anonymityset and if the anonymity set changes with time due to unsynchronizedparticipants, then the anonymity technique becomesprone to traffic analysis attacks. in this paper, we areinterested in the statistical properties of the disclosure attack,a newly suggested traffic analysis attack on the mixes.our goal is to provide analytical estimates of the number ofobservations required by the disclosure attack and to identifyfundamental (but avoidable) weak operational modes'of the mixes and thus to protect users against a traffic analysisby the disclosure attack.
analyzing consistency of security policies. abstract: we discuss the development of a methodology for reasoning about properties of security policies. we view a security policy as a special case of regulation which specifies what actions some agents are permitted, obliged or forbidden to perform and we formalize a policy by a set of deontic formulae. we first address the problem of checking policy consistency and describe a method for solving it. the second point we are interested in is how to query a policy to know the actual norms which apply to a given situation. in order to provide the user with consistent answers, the normative conflicts which may appear in the policy must be solved. for doing so, we suggest using the notion of roles and define priorities between roles.
using conservation of flow as a security mechanism in network protocols. the law of conservation of flow, which states that an input must either be absorbed or sent on as an output (possibly with modification), is an attractive tool with which to analyze network protocols for security properties. one of its uses is to detect disruptive network elements that launch denial of service attacks by absorbing or discarding packets. its use requires several assumptions about the protocols being analyzed. in this paper, we examine the watchers algorithm to detect misbehaving routers. we show that it uses conservation of flow without sufficient verification of its assumptions, and can consequently be defeated. we suggest improvements to make the use of conservation of flow valid.
cryptographic security for mobile code. abstract: this paper addresses the protection of mobile code against cheating and potentially malicious hosts. we point out that the recent approach based on computing with "encrypted functions" is limited to the case where only the code originator learns the result of the computation and the host running the code must not notice anything at all. we argue that if the host is to receive some output of the computation, then securing mobile code requires minimal trust in a third party. tamper-proof hardware installed on each host has been proposed for this purpose. in this paper we introduce a new approach for securely executing (fragments of) mobile code that relies on a minimally trusted third party. this party is a generic independent entity, called the secure computation service, which performs some operations on behalf of the mobile application, but does not learn anything about the encrypted computation. because it is universal, the secure computation service needs to be only minimally trusted and can serve many different applications. we present a protocol based on tools from theoretical cryptography that is quite practical for computing small functions.
semantics-aware malware detection. a malware detector is a system that attempts to determine whether a program has malicious intent. in order to evade detection, malware writers (hackers) frequently use obfuscation to morph malware. malware detectors that use a pattern-matching approach (such as commercial virus scanners) are susceptible to obfuscations used by hackers. the fundamental deficiency in the pattern-matching approach to malware detection is that it is purely syntactic and ignores the semantics of instructions. in this paper, we present a malware-detection algorithm that addresses this deficiency by incorporating instruction semantics to detect malicious program traits. experimental evaluation demonstrates that our malware-detection algorithm can detect variants of malware with a relatively low run-time overhead. moreover, our semantics-aware malware detection algorithm is resilient to common obfuscations used by hackers.
searching for a solution: engineering tradeoffs and the evolution of provably secure protocols. tradeoffs are an important part of engineering security. protocol security is important. so are efficiency and cost. this paper provides an early framework for handling such aspects in a uniform way based on combinatorial optimization techniques. ban logic is viewed as both a specification and proof system and as a `protocol programming language'. the paper shows how evolutionary search in the form of genetic algorithms can be utilized to `grow' correct and efficient ban protocols and shows how goals and assumptions can co-evolve, effectively engaging in `specification synthesis'.
surviving information warfare attacks on databases. abstract: we consider the problem of surviving information warfare attacks on databases. we adopt a fault tolerance approach to the different phases of an attack. to maintain precise information about the attack, we mark data to reflect the severity of detected damage as well as the degree to which the damaged data has been repaired. in the case of partially repaired data, integrity constraints might be violated, but data is nonetheless available to support mission objectives. we define a notion of consistency suitable for databases in which some information is known to be damaged, and other information is known to be only partially repaired. we present a protocol for normal transactions with respect to the damage markings and show that consistency preserving normal transactions maintain database consistency in the presence of damage. we present an algorithm for taking consistent snapshots of databases under attack. the snapshot algorithm has the virtue of not interfering with countermeasure transactions.
towards constant bandwidth overhead integrity checking of untrusted data. we present an adaptive tree-log scheme to improve the performance of checking the integrity of arbitrarily-large untrusted data, when using only a small fixed-sized trusted state. currently, hash trees are used to check the data. in many systems that use hash trees, programsperform many data operations before performing a critical operation that exports a resultoutside of the program's execution environment. the adaptive tree-log scheme we present uses this observation to harness the power of the constant runtime bandwidth overhead of a log-based scheme. for all programs, the adaptive tree-log scheme's bandwidth overhead is guaranteed to never be worse than a parameterizable worst case bound. furthermore, for all programs, as the average number of times the program accesses data between critical operations increases, the adaptive tree-log scheme's bandwidth overhead moves from a logarithmic to a constant bandwidth overhead.
ensuring atomicity of multilevel transactions. ensuring atomicity is a major outstanding problem with present methods of handling multilevel transactions. the chief difficulty is that a high section of a transaction may be unable to complete due to violations of the integrity constraints, and a rollback of sections can be exploited to implement a covert channel. we define a notion of semantic atomicity which guarantees that either all or none of the sections of a transaction are present in any history. the notion of correct executions in our model is based on semantic correctness -- that is, maintenance of integrity constraints -- rather than serializability. we give a method whereby the application developer can statically analyze the set of transactions in the application and determine if the set ensures semantic atomicity and other desirable properties.
using views in a multilevel secure database management system. the use of database views in databasemanagement systems that enforce user level discretionaryand nondiscretionary access controlpolicies is discussed. this discussion involvesseveral issues such as how should views beclassified?, what types of mechanisms should beused to define views?, etc. mapping betweenviews, view updating, and aggregation andinference problems are also discussed.
sd3: a trust management system with certified evaluation. abstract: we introduce sd3, a trust management system consisting of a high-level policy language, a local policy evaluator, and a certificate retrieval system. a unique feature of sd3 is its certified evaluator: as the evaluator computes the answer to a query, it also computes a proof that the answer follows from the security policy. before the answer is returned, the proof is passed through a simple checker, and incorrect proofs are reported as errors. the certified evaluator reduces the trusted computing base and greatly increases our confidence that the answers produced by the evaluator follow from the specification, despite complex optimizations. to illustrate sd3's capabilities, we show how to implement a secure name service, similar to dnssec, entirely in sd3.
privacy technology lessons from healthcare. the probability that information will be abused depends both on its value and on the number of people who have access. the modern trend to ever-larger databases increases both of these risk factors at the same time. compartmented security polices can solve many of the technical issues, and there are applications - such as healthcare - where they have been developed in some detail. however, the big problem is not technical; it is legal and regulatory. insurers, employers and governments will not adopt compartmented systems, or will allow them to be adopted only in places such as hospitals, which are not where the real threats lie.
a more efficient use of delta-crls. delta-certificate revocation lists (delta-crls) were designed to provide a more efficient way to distribute certificate status information. however, as this paper shows, in some environments the benefits of using delta-crls will be minimal if delta-crls are used as was originally intended. this paper provides an analysis of delta-crls that demonstrates the problems associated with issuing delta-crls in the ¿traditional¿ manner. a new, more efficient technique for issuing delta-crls, sliding window delta-crls, is presented.
an approach to indentification of minimum tcb requirements for various threat/risk environments. a gross identification of threats andrisks based on a data classificationenvironment and the minimum clearancelevel of individuals using a system isrelated to the levels identified in thedodcsc trusted computer evaluationcriteria. a proposed set of minimum tcblevels for given threat risk environmentsis identified.
a logic for constraint-based security protocol analysis. we propose ps-ltl, a pure-past security linear temporal logic that allows the specification of a variety of authentication, secrecy and data freshness properties. furthermore, we present a sound and complete decision procedure to establish the validity of security properties for symbolic execution traces, and show the integration with constraintbased analysis techniques.
a security policy model for clinical information systems. abstract: the protection of personal health information has become a live issue in a number of countries, including the usa, canada, britain and germany. the debate has shown that there is widespread confusion about what should be protected, and why. designers of military and banking systems can refer to bell & lapadula (1973) and clark & wilson (1987) respectively, but there is no comparable security policy model that spells out clear and concise access rules for clinical information systems. in this article, we present just such a model. it was commissioned by doctors and is driven by medical ethics; it is informed by the actual threats to privacy, and reflects current best clinical practice. its effect is to restrict both the number of users who can access any record and the maximum number of records accessed by any user. this entails controlling information flows across rather than down and enforcing a strong notification property. we discuss its relationship with existing security policy models, and its possible use in other applications where information exposure must be localised; these range from private banking to the management of intelligence data.
a basis for secure communication in large distributed systems. large distributed systems have properties that, from the point of view of security distinguish them from lan-based systems. we describe these differences and show the security mechanisms found in current distributed systems are not well-suited to large system. we propose a secure communication architecture for large systems that puts security below the transport level. we argue that this is preferable to putting it at higher levels, and that in fact it can simplify and improve the performance of transport protocols.
a safety-oriented platform for web applications. the web browser has become the dominant interface to a broad range of applications, including online banking, web-based email, digital media delivery, gaming, and ecommerce services. early web browsers provided simple access to static hypertext documents. in contrast, modern browsers serve as de facto operating systems that must manage dynamic and potentially malicious applications. unfortunately, browsers have not properly adapted to their new role. as a consequence, they fail to provide adequate isolation across applications, exposing both users and web services to attack.
formal treatment of certificate revocation under communal access control. abstract: the conventional approach to distributed access-control (ac) tends to be server-centric. under this approach, each server establishes its own policy regarding the use of its resources and services by its clients. the choice of this policy, and its implementation, are generally considered the prerogative of each individual server. this approach to access-control may be appropriate for many current client-server applications, where the server is an autonomous agent, in complete charge of its resources. but it is not suitable for the growing class of applications where a group of servers, and sometimes their clients, belong to a single enterprise, and are subject to the enterprise-wide policy governing them all. one may not be able to entrust such an enterprise-wide policy to the individual servers, for two reasons: first, it is hard to ensure that an heterogeneous set of servers implement exactly the same policy. second, as we will demonstrate, an ac policy can have aspects that cannot, in principle, be implemented by servers alone. as argued in a previous paper [11], what is needed in this situation is a concept of communal policy that governs the interaction between the members of a distributed community of agents involved in some common activity, along with a mechanism that provides for the explicit formulation of such policies, and for their scalable enforcement. this paper focuses on the communal treatment of expiration and revocation of the digital certificates used for the authentication of the identity and roles of members of the community.
a secure and reliable bootstrap architecture. abstract: in a computer system, the integrity of lower layers is typically treated as axiomatic by higher layers. under the presumption that the hardware comprising the machine (the lowest layer) is valid, the integrity of a layer can be guaranteed if and only if: (1) the integrity of the lower layers is checked and (2) transitions to higher layers occur only after integrity checks on them are complete. the resulting integrity "chain" inductively guarantees system integrity. when these conditions are not met, as they typically are not in the bootstrapping (initialization) of a computer system, no integrity guarantees can be made, yet these guarantees are increasingly important to diverse applications such as internet commerce, security systems and "active networks". in this paper, we describe the aegis architecture for initializing a computer system. it validates integrity at each layer transition in the bootstrap process. aegis also includes a recovery process for integrity check failures, and we show how this results in robust systems.
using programmer-written compiler extensions to catch security holes. this paper shows how system-specific static analysis can find securityerrors that violate rules such as ``integers from untrusted sourcesmust be sanitized before use'' and ``do not dereference user-suppliedpointers.''in our approach, programmers write system-specificextensions that are linked into the compiler and check their code forerrors.we demonstrate the approach's effectiveness by using it tofind over 100 security errors in linux and openbsd, over 50 of whichhave led to kernel patches.an unusual feature of our approach is theuse of methods to automatically detect when we miss code actions thatshould be checked.
alert correlation in a cooperative intrusion detection framework. this paper presents the work we have done within the mirador project to design crim, a cooperative module for intrusion detection systems (ids). this module implements functions to manage, cluster, merge and correlate alerts. the clustering and merging functions recognize alerts that correspond to the same occurrence of an attack and create a new alert that merge data contained in these various alerts. experiments show that these functions significantly reduce the number of alerts. however, we also observe that alerts we obtain are still too elementary to be managed by a security administrator. the purpose of the correlation function is thus to generate global and synthetic alerts. this paper focuses on the approach we suggest to design this function.
mixminion: design of a type iii anonymous remailer protocol. we present mixminion, a message-based anonymous remailerprotocol with secure single-use reply blocks. mixnodes cannot distinguish mixminion forward messages fromreply messages, so forward and reply messages share thesame anonymity set. we add directory servers that allowusers to learn public keys and performance statistics of participatingremailers, and we describe nymservers that providelong-term pseudonyms using single-use reply blocksas a primitive. our design integrates link encryption betweenremailers to provide forward anonymity. mixminionworks in a real-world internet environment, requires littlesynchronization or coordination between nodes, and protectsagainst known anonymity-breaking attacks as well asor better than other systems with similar design parameters.
intransitive non-interference for cryptographic purpose. information flow and non-interference have recentlybecome very popular concepts for expressing both integrityand privacy properties. because of the enormouspotential of transmitting information using probabilisticmethods of cryptography, interest arose in capturingprobabilistic non-interference. we investigate the notionof intransitive probabilistic non-interference in reactivesystems, i.e., downgrading of probabilistic informationand detection of probabilistic information flowby one or more involved third parties. based on concreteexamples, we derive several definitions that comprisecryptography-related details like error probabilities andcomputational restrictions. this makes the definitionsapplicable to systems involving real cryptography. detectionof probabilistic information flow is significantlymore complicated to define if several third parties areinvolved because of the possibilities of secret sharing.we solve this problem by graph-theoretic techniques.
relating symbolic and cryptographic secrecy. we investigate the relation between symbolic and cryptographic secrecy properties for cryptographic protocols. symbolic secrecy of payload messages or exchanged keys is arguably the most important notion of secrecy shown with automated proof tools. it means that an adversary restricted to symbolic operations on terms can never get the entire considered object into its knowledge set. cryptographic secrecy essentially means computational indistinguishability between the real object and a random one, given the view of a much more general adversary. in spite of recent advances in linking symbolic and computational models of cryptography, no relation for secrecy under active attacks is known yet. for exchanged keys, we show that a certain strict symbolic secrecy definition over a specific dolev-yao-style cryptographic library implies cryptographic key secrecy for a real implementation of this cryptographic library. for payload messages, we present the first general cryptographic secrecy definition for a reactive scenario. the main challenge is to separate secrecy violations by the protocol under consideration from secrecy violations by the protocol users in a general way. for this definition we show a general secrecy preservation theorem under reactive simulatability, the cryptographic notion of secure implementation. this theorem is of independent cryptographic interest. we then show that symbolic secrecy implies cryptographic payload secrecy for the same cryptographic library as used in key secrecy. our results thus enable existing formal proof techniques to establish cryptographically sound proofs of secrecy for payload messages and exchanged keys.
binder, a logic-based security language. we introduce the concept of a security language, used to expresssecurity statements in a distributed system. most existing securitylanguages encode security statements as schematized data structures,such as acls and x.509 certificates. in contrast, binder is an openlogic-based security language that encodes security statements ascomponents of communicating distributed logic programs. binder programscan be more expressive than statements in standard security languages,and the meanings of standard security constructs and operations such ascertificates and delegation are simplified and clarified by theirformulation in binder. translation into binder has been used to explorethe design of other new and existing security languages.
a security infrastructure for distributed java applications. we describe the design and implementation of a security infrastructure for a distributed java application. this work is inspired by sdsi/spki, but has a few twists of its own. we define logic for access control, such that access is granted if a proof that it should be granted is derivable in the logic. our logic supports linked local name spaces, privilege delegation across administrative domains, and attribute certificates. we use ssl to establish secure channels through which principals can ¿speak¿, and have implemented our access control system in java. while we implemented our infrastructure for the placeless documents system, our design is applicable to other applications as well. we discuss general issues related to building secure, distributed java applications that we discovered.
joint encryption and error-correction coding. this paper considers the problem of joint encryptionand error-correction coding and proposesa solution using d-sequences, which are decimal'expansions of fractions. the encryption operationconsidered is equivalent to exponentiation whichforms the basis of several public-key schemes.several new results on d-sequences are also presented which make the applications to encryptionand error coding possible.