5,067 research outputs found
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Data-Driven Generalized Integer Aperture Bootstrapping for Real-Time High Integrity Applications
A new method is developed for integer ambiguity
resolution in carrier-phase differential GPS (CDGPS) positioning.
The method is novel in that it is (1) data-driven, (2) generalized
to include partial ambiguity resolution, and (3) amenable to a
full characterization of the prior and posterior distributions of
the three-dimensional baseline vector that results from CDGPS.
The technique is termed generalized integer aperture bootstrapping
(GIAB). GIAB improves the availability of integer
ambiguity resolution for high-integrity, safety-critical systems.
Current high-integrity CDGPS algorithms, such as EPIC and
GERAFS, evaluate the prior risk of position domain biases due to
incorrect integer ambiguity resolution without further validation
of the chosen solution. This model-driven approach introduces
conservatism which tends to reduce solution availability. Common
data-driven ambiguity validation methods, such as the ratio test,
control the risk of incorrect ambiguity resolution by shrinking
an integer aperture (IA), or acceptance region. The incorrect
fixing risk of current IA methods is determined by functional
approximations that are inappropriate for use in safety-of-life
applications. Moreover, generalized IA (GIA) methods incorrectly
assume that the baseline resulting from partial ambiguity resolution
is zero mean. Each of these limitations is addressed by
GIAB, and the claimed improvements are validated by Monte
Carlo simulation. The performance of GIAB is then optimized by
tuning the integer aperture size to maximize the prior probability
of full ambiguity resolution. GIAB is shown to provide higher
availability than EPIC for the same integrity requirements.Aerospace Engineering and Engineering Mechanic
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A two‐step authentication framework for Mobile ad hoc networks
The lack of fixed infrastructure in ad hoc networks causes nodes to rely more heavily on peer nodes for communication. Nevertheless, establishing trust in such a distributed environment is very difficult, since it is not straightforward for a node to determine if its peer nodes can be trusted. An additional concern in such an environment is with whether a peer node is merely relaying a message or if it is the originator of the message. In this paper, we propose an authentication approach for protecting nodes in mobile ad hoc networks. The security requirements for protecting data link and network layers are identified and the design criteria for creating secure ad hoc networks using several authentication protocols are analyzed. Protocols based on zero knowledge and challenge response techniques are presented and their performance is evaluated through analysis and simulation
LightChain: A DHT-based Blockchain for Resource Constrained Environments
As an append-only distributed database, blockchain is utilized in a vast
variety of applications including the cryptocurrency and Internet-of-Things
(IoT). The existing blockchain solutions have downsides in communication and
storage efficiency, convergence to centralization, and consistency problems. In
this paper, we propose LightChain, which is the first blockchain architecture
that operates over a Distributed Hash Table (DHT) of participating peers.
LightChain is a permissionless blockchain that provides addressable blocks and
transactions within the network, which makes them efficiently accessible by all
the peers. Each block and transaction is replicated within the DHT of peers and
is retrieved in an on-demand manner. Hence, peers in LightChain are not
required to retrieve or keep the entire blockchain. LightChain is fair as all
of the participating peers have a uniform chance of being involved in the
consensus regardless of their influence such as hashing power or stake.
LightChain provides a deterministic fork-resolving strategy as well as a
blacklisting mechanism, and it is secure against colluding adversarial peers
attacking the availability and integrity of the system. We provide mathematical
analysis and experimental results on scenarios involving 10K nodes to
demonstrate the security and fairness of LightChain. As we experimentally show
in this paper, compared to the mainstream blockchains like Bitcoin and
Ethereum, LightChain requires around 66 times less per node storage, and is
around 380 times faster on bootstrapping a new node to the system, while each
LightChain node is rewarded equally likely for participating in the protocol
LightBox: Full-stack Protected Stateful Middlebox at Lightning Speed
Running off-site software middleboxes at third-party service providers has
been a popular practice. However, routing large volumes of raw traffic, which
may carry sensitive information, to a remote site for processing raises severe
security concerns. Prior solutions often abstract away important factors
pertinent to real-world deployment. In particular, they overlook the
significance of metadata protection and stateful processing. Unprotected
traffic metadata like low-level headers, size and count, can be exploited to
learn supposedly encrypted application contents. Meanwhile, tracking the states
of 100,000s of flows concurrently is often indispensable in production-level
middleboxes deployed at real networks.
We present LightBox, the first system that can drive off-site middleboxes at
near-native speed with stateful processing and the most comprehensive
protection to date. Built upon commodity trusted hardware, Intel SGX, LightBox
is the product of our systematic investigation of how to overcome the inherent
limitations of secure enclaves using domain knowledge and customization. First,
we introduce an elegant virtual network interface that allows convenient access
to fully protected packets at line rate without leaving the enclave, as if from
the trusted source network. Second, we provide complete flow state management
for efficient stateful processing, by tailoring a set of data structures and
algorithms optimized for the highly constrained enclave space. Extensive
evaluations demonstrate that LightBox, with all security benefits, can achieve
10Gbps packet I/O, and that with case studies on three stateful middleboxes, it
can operate at near-native speed.Comment: Accepted at ACM CCS 201
A Secure and Reliable Bootstrap Architecture
In a computer system, the integrity of lower layers is treated as axiomatic by higher layers. Under the presumption that the hardware comprising the machine (the lowest layer) is valid, 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, intrusion detection 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. We discuss our prototype implementation for the IBM personal computer (PC) architecture, and show that the cost of such system protection is surprisingly small
The Value of User-Visible Internet Cryptography
Cryptographic mechanisms are used in a wide range of applications, including
email clients, web browsers, document and asset management systems, where
typical users are not cryptography experts. A number of empirical studies have
demonstrated that explicit, user-visible cryptographic mechanisms are not
widely used by non-expert users, and as a result arguments have been made that
cryptographic mechanisms need to be better hidden or embedded in end-user
processes and tools. Other mechanisms, such as HTTPS, have cryptography
built-in and only become visible to the user when a dialogue appears due to a
(potential) problem. This paper surveys deployed and potential technologies in
use, examines the social and legal context of broad classes of users, and from
there, assesses the value and issues for those users
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