In this research, we propose an explanatory model that learns combinations of microbiome signatures that help predict reduced multidrug resistance (MDR) of disease-causing pathogens. A twin regression network in our model provides a means for estimating the MDR presence using microbiome samples. Further, we extend our model by using a backtracking approach that determines the effect of specific microbiome signatures on the prevalence of MDR, to identify potential beneficial combinations. Using high-throughput Illumina sequencing of the 16SrRNA gene data from 41 pastured poultry flocks in southeastern U.S. farms, the regression model identifies the factors influencing MDR prevalence in common foodborne pathogens (Salmonella, Campylobacter, and Listeria) at different stages of poultry growth.

Within cloud computing containerization has become ubiquitous. As the availability of pre-built containers increases there is a need for methods capable of efficiently securing large repositories of software containers. We present a “Trustworthy Container Repository” (TCR) system which provides security assurances (confidentiality, integrity, and authenticity) regarding such a repository in a scalable manner. Trust within the TCR architecture is rooted in a low-complexity, tamper-resistant trusted module, which leverages index-ordered Merkle trees (IOMTs) to efficiently track a large number of container images and provide assurances of repository integrity to its users. The key contributions of the study are, identification of the required security model, a novel TCR data-structure, and verifiable algorithms to operate on it. Through experiment, we observe closely logarithmic time complexity of the proposed system up to a high container count ( N = 2 25 ≈ 10 7 ).

Securing any MANET routing protocol requires measures to ensure that routing information advertised by a node (to its neighbors) is consistent with routing information assimilated by a node (from its neighbors). We investigate a minimal trusted computing base (TCB) for MANET nodes to ensure this requirement. We outline low complexity TCB functions which can be executed inside trustworthy boundaries of resource limited trustworthy MANET modules (TMM). The TCB functions are used to maintain a table of active neighbors, create routing records (RR), authenticate RRs to TMMs in neighboring nodes, receive authenticated RRs, and update RRs, subject to simple rules. Even while the dynamic RR database of every node is stored outside the TMM, by storing the root of an index ordered Merkle hash tree (IOMT) the TMMs can ensure that nodes cannot modify, replay or even hide RRs.

Probabilistic key predistribution schemes (P-KPSs) which place modest demands on hardware are good candidates for securing interactions between resource limited computers. Collusion susceptible P-KPSs are trade-offs between security and complexity. Some facets of complexity include computation, bandwidth, and storage overhead. Metrics for security include resistance to passive eavesdropping attacks, and active message injection attacks. The contributions of this paper are three-fold: 1) a novel P-KPS, the subset keys and identity tickets (SKIT) scheme; 2) a generic KPS model to facilitate comparison of various facets of the complexity of key predistribution schemes; and 3) a new security model to describe the resistance of P-KPSs to active message-injection attacks. The two models are used to showwhySKIT has many compelling advantages over existing P-KPSs in the literature. In particular, while placing lower demands on computation, bandwidth and storage overhead, SKIT realizes substantial improvements in resistance to passive and active attacks.

Nodes forming mobile ad hoc networks (MANET) can be logically partitioned into 1) a selfish user agent serving the interests of the end user (owner) and 2) a selfless network agent serving the broad interests of the network. The routing tasks performed by any mobile node can then be shared between physically distinct user and network agents. The user agent could be a laptop, PDA or any such mobile network device. The network agent can be a secure co-processor in the form of a SIM card. In the interests of protecting the integrity of the network agent and keeping its cost low, it is desirable to reduce its complexity. We identify four broad classes of attacks that can be perpetrated by the user agents on resource constrained network agents, and propose low complexity strategies within the scope of network agents, to overcome such attacks and ensure the integrity of the routing protocol.

Classical sensor network applications involve deployments of a large number of resource constrained wireless sensors in conjunction with a few "more capable" proxy devices. Many key distribution schemes employing only symmetric cryptographic primitives have been proposed for establishing pairwise secrets between sensors. At one end of the spectrum are Kerberos-like approaches where proxy devices are trusted with secrets of sensors, and mediate establishment of pairwise secrets between sensors. At the other end of the spectrum are many collusion susceptible key pre-distribution schemes that do not rely on the proxy devices for establishment of pairwise secrets. In this paper we propose a third approach where while the proxies aid the sensors in the process of establishment of pairwise secrets, the proxy devices are not trusted with the secrets of the sensors.

Some important requirements of key distribution schemes for many emerging applications involving resource constrained devices (for example, ad hoc and sensor networks) are 1) low complexity; 2) the ability to support unmediated establishment of security associations and 3) scalability. We propose a novel key distribution scheme based on an elegant scheme proposed by Leighton and Micali (1994). While the scheme in (Leighton and Micali, 1994) was intended to be an alternative to Kerberos (employing a trusted server for mediation), the proposed modifications are towards realizing a scheme for nonmediated establishment of pairwise secrets. We enumerate several compelling advantages of the proposed scheme over existing schemes in the literature.

Ariadne is a popular secure ad hoc routing protocol based on the dynamic source routing (DSR) protocol. While Ariadne was designed to be capable of detecting attacks by non colluding attackers, it does not include measures to identify or narrow down perpetrators responsible for such attacks. We propose some modifications to Ariadne to improve its resiliency, by affording the ability to identify and route around malicious nodes.

Trustworthy computing modules like secure coprocessors (ScP) are already in extensive use today, albeit limited predominantly to scenarios where constraints on cost is not a serious limiting factor. However, inexpensive trustworthy computers are required for many evolving application scenarios. The problem of realizing inexpensive ScPs for large-scale networks consisting of low-complexity devices have not received adequate consideration thus far. We introduce two strategies toward realizing low-cost ScPs. The first is the decrypt only when necessary (DOWN) policy, which can substantially improve the ability of low-cost ScPs to protect their secrets. The DOWN policy relies on the ability to operate with fractional parts of secrets. Taking full advantage of the DOWN policy requires consideration of the nature of computations performed with secrets and even the mechanisms employed for distribution of secrets. We discuss the feasibility of extending the DOWN policy to various asymmetric and symmetric cryptographic primitives. The second is cryptographic authentication strategies which employ only symmetric cryptographic primitives, based on novel ID-based key predistribution schemes that demand very low complexity of operations to be performed by the ScP and can take good advantage of the DOWN policy.

Ensuring cryptographic integrity of the route discovery process in on demand ad hoc routing approaches like dynamic source routing (DSR) require the ability to verify that no nodes have been deleted from the path, and no node can be inserted in the path without a valid authentication. We discuss the need for early detection of inconsistencies involving inserted or deleted nodes in route request (RREQ) packets and investigate the challenges associated with catering for this requirement. We propose an efficient strategy to achieve this employing only symmetric cryptographic primitives, which is made possible due to a recently proposed multi-source broadcast encryption scheme. We outline a protocol for secure route discovery in DSR that employs such a security primitive, and provide quantitative estimates (through simulations) of gains that can be achieved by early detection of inconsistent RREQs.

Assuring cryptographic integrity of mutable fields in any on-demand ad hoc routing protocol is more challenging than that of non mutable fields. We propose an efficient authentication strategy for this purpose, which leverages a proposed broadcast encryption (BE) scheme. We investigate some shortcomings of SAODV, a popular secure extension of the ad hoc on-demand distance vector (AODV) protocol and suggest some modifications to the protocol to overcome the shortcomings. The modifications include proactive maintenance of a secure reliable delivery neighborhood (RDN) by each node and the use of the BE based authentication strategy for mutable fields.

For many evolving application scenarios like ubiquitous and autonomic computing systems, trustworthy computing solutions are essential. However the fact that the autonomic elements that may take part in such networks may be (1) severely resource constrained, and that (2) the sheer scale of such devices may also place constraints on their cost, calls for inexpensive, low complexity (but nevertheless trustworthy) computing modules, or secure co-processors (ScP). We propose two synergistic strategies for the realization of very low complexity, inexpensive ScPs. The first is a simple security policy, decrypt only when necessary (DOWN). The second is the utilization of untrusted external resources to improve the security of very low complexity ScPs. We point out some very desirable properties of probabilistic key pre-distribution schemes (PKPS) that can take good advantage of the DOWN policy and simultaneously make use of external resources, to render the problem of their susceptibility to collusions irrelevant.

With rapidly decreasing cost of storage, even for mobile computing applications involving PDAs / mobile phones storage (using flash memory) is an inexpensive resource. We introduce a novel probabilistic key predistribution scheme (PKPS) I-HARPS which can make good use of this inexpensive resource to improve security. I-HARPS is a combination of random subset allocation schemes first proposed by Dyer et al [1] in 1995, and the escrowed master key based key distribution scheme proposed by Leighton and Micali in 1993 [2]. While PKPSs have received substantial attention recently in the context of highly resource constrained sensor networks, we argue that the fact that I-HARPS can resist coalitions of even millions of nodes with very low computational complexity, and very reasonable storage requirements, can significantly expand the scope of applications of PKPSs.

We introduce a novel broadcast authentication (BA) scheme especially well suited for nodes forming multihop ad hoc networks (MH-AHN). The proposed BA scheme is based on a recently proposed probabilistic key pre-distribution scheme (KPS), HARPS. Apart from a substantial performance improvements over existing BA schemes, the proposed technique offers many possible trade-offs (bandwidth-computation, and bandwidth-storage) for improving security.

One-way links are an unavoidable reality in wireless channels. The detrimental effects of one way links on many routing strategies, including the dynamic source routing protocol (DSR), have been investigated by many researchers. Apart from reducing the efficiency of DSR, we point out that disregarding possible one-way links also has some implications on the security of secure DSR extensions. Most secure extensions of DSR rely on the assumption that all links are bidirectional. We point out proactive strategies to indicate one-way links in route request (RREQ) packets to limit their use, with the intention of simultaneously improving the efficiency and security of secure DSR protocols.

We introduce hashed random preloaded subsets (HARPS), a highly scalable key predistribution (KPD) scheme employing only symmetric cryptographic primitives. HARPS is ideally suited for resource constrained nodes that need to operate for extended periods without active involvement of a trusted authority (TA), as is usually the case for nodes forming ad hoc networks (AHNs). HARPS, a probabilistic KPD scheme, is a generalization of two other probabilistic KPDs. The first, random preloaded subsets (RPSs), is based on random intersection of keys preloaded in nodes. The second, proposed by Leighton and Micali (LM) is a scheme employing repeated applications of a cryptographic hash function. We investigate many desired properties of HARPS like scalability, computational and storage efficiency, flexibility in deployment modes, renewability, ease of extension to multicast scenarios, ability to cater for broadcast authentication, broadcast encryption, etc., to support its candidacy as an enabler for ad hoc network security. We analyze and compare the performance of the three schemes and show that HARPS has significant advantages over other KPDs, and in particular, over RPS and LM.

Any key pre-distribution (KPD) scheme is inherently a trade-off between complexity and security. By sacrificing some security (KPD schemes need some assurance of the ability to limit sizes of attacker coalitions), KPD schemes gain many advantages. We argue that random KPD schemes, in general, perform an "advantageous" trade-off which renders them more suitable for practical large scale deployments of resource constrained nodes. We introduce a novel random KPD scheme, hashed random preloaded subsets (HARPS), which turns out to be a generalization of two other random KPD schemes, random preloaded subsets (RPS) and a scheme proposed by T. Leighton and S. Micali (LM). All three schemes have probabilistic measures for the "merit" of the system. We analyze and compare the performance of the three schemes. We show that HARPS has significant advantages over other KPD schemes, and in particular, over RPS and LM.

This paper introduces the measure of information as a new criterion for the performance analysis of routing algorithms in wireless sensor networks. We argue that since the objective of a sensor network is to estimate a two dimensional random field, a routing algorithm must maximize information flow about the underlying field over the lifetime of the sensor network. We develop two novel algorithms, MIR (maximum information routing) and CMIR (conditional maximum information routing) designed to maximize information flow, and present a comparison of the algorithms to a previously proposed algorithm-MREP (maximum residual energy path) through simulations. We show that the proposed algorithms give significant improvement in terms of information flow, when compared to MREP.

We analyze quantization based embedding and detection schemes in terms of the data hiding framework we have introduced (Ref.1, 2). This framework enables a better connection between analytical results and practical designs. We lay out the performance evaluation criteria and present comparison results for scalar quantization based data hiding techniques. Embedder-detector designs are evaluated based on three key issues. These are: (1) the type of post-processing employed at the embedder; (2) the form of demodulation; (3) the criteria used to optimize embedding-detection parameters. Data hiding methods are compared based on rate, correlation, and probability of error performance merits.

We propose a system for digital rights management (DRM) which facilitates large scale deployments of heterogeneous devices, manufactured by different vendors, to interact and authenticate with each other securely in order to ensure fairness of transactions. The proposed system allows for both pluggable (and transferable) security modules for end-user authentication and built-in (non-transferable) security modules for mutual authentication of compliant devices (manufactured by different vendors). For the underlying security mechanism we propose the use of a recently proposed random key predistribution scheme, HARPS (Hashed Random Preloaded Subsets).

We explore the problem of proving ownership or origin of multimedia content like image/video or audio signals through watermarking. The need for watermarking arises out of the insufficiency of present copyright laws for claiming ownership of digital content. Watermarking schemes however, are threatened by counterfeit attacks, which primarily use the freedom available in choice of signature or choice of the watermarking method. A restrictive protocol for watermarking could go a long way in rendering counterfeit attacks extremely difficult. We suggest a comprehensive protocol as an extension of the one suggested by Craver et al. , that makes it possible for the true owner to claim ownership unambiguously, while making it extremely difficult for a pirate to do so.

The problem of efficient data hiding robust to lossy compression is divided into two subproblems. First is to maximize the resource-which is the permitted distortion of images. The second is the efficient use of the resource by means of sophisticated signaling techniques . We conclude that a good solution to the first problem is choosing magnitude discrete Fourier transform as the domain in which the message signal is embedded. For the signaling method we use a sophisticated signaling technique, using periodic functions to tile the space with signal constellations.

The nature of mobile ad hoc networks (MANET), demands stringent requirements on primitives that could be used to secure such networks. Mobility imposes restrictions on memory and processor requirements due to limited battery life. The ad hoc nature warrants schemes that could operate for extended periods without referring to a trusted authority (TA). Additionally, any enabling scheme for security should be able to scale well. We introduce a novel key management scheme, RPS - random preloaded subset key distribution - which satisfies all the above requirements. More specifically, RPS is an n-secure r-conference key predistribution scheme. While most of the previously reported key predistribution schemes also meet all the stringent requirements, RPS has many inherent advantages. In this paper we investigate the applicability of RPS in securing MANETs.

In this paper, we analyze oblivious (blind) information hiding methods from a new perspective. In 1983, Costa introduced a communications framework that also applies to oblivious information hiding. We present an alternate and equivalent framework by carrying out the channel dependent nature of the optimal encoder in a different manner. Within the proposed framework, decoder structure is simplified, although in effect it's a slender advantage compared to overall complexity. This interpretation provides a better connection between the analytical results and practical designs. We evaluate the practical embedding-detection schemes employing scalar quantization procedures along with thresholding and distortion compensation types of processings from this perspective. Furthermore, we justify the assumptions for the optimality of the two types of processings.

In a mature watermarking and steganography application, the security should lie in the unknow random keys not in the embedding algorithms. In this paper, the problem of the selection of watermarking random sequences is investigated. In the widely used Spread Spectrum modulation schemes, a white sequence and a Low-Pass (LP) type sequences are analyzed, including its security level and synchronization requirements. It is found that the white independent is more secure but not robust against LP attack. Also it is not energy efficient. Actually The random sequence selection is usually the tradeoff between these factors. To be resilient to the removal attacks, the watermark spectrum should be similar to the spectrum of the cover signal. A watermarking sequence with fixed amplitude spectrum shape and random phase is proposed in the last part of the paper and its properties are discussed in detail.

Compression is the most common application that an forms of multimedia data undergo. Lossy nature of the compression due to the use of quantizers should be taken into account by the watermarking technique employed. In this paper, we present a data hiding scheme that incorporates the embedding with the quantization of lossy compression. We show that embedder-detector sets making use of compression scheme's quantization characteristics have better payload and lower compression bit rates. We also optimized the system parameters that maximize the hiding rate at different compression levels.

Robustness to compression is a basic requirement for any data hiding scheme. We concentrate on MP3 resistant oblivious data hiding. First the MP3 compression algorithm is briefly introduced. We then propose three effective data hiding schemes, where the message is embedded in amplitude, DFT phase domain, and noisy components, respectively. All these schemes demonstrate robustness to MP3 compression.

In oblivious steganography, host noise suppression is a great concern as the watermark signal energy is usually much less than that of the host signal. We model the data hiding as a more general H0/H1 hypothesis testing problem. Decision making is based on the statistical distinction between H0 and H1. A simple embedding scheme, viz., set partitioning, is proposed. The coefficients are divided into two sets to represent bit value 1 and 0. The average distortion introduced is calculated. Its optimum and suboptimal detection is discussed in detail. Analysis and simulation studies show improvement over existing schemes.

In this paper, we present an information-theoretic approach to obtain an estimate of the number of bits that can be hidden in still images, or, the capacity of the data-hiding channel.We show how the addition of the message signal or signature in a suitable transform domain rather than the spatial domain can significantly increase the channel capacity. Most of the state-of-the-art schemes developed thus far for data-hiding have embedded bits in some transform domain, as it has always been implicitly understood that a decomposition would help. Though most methods reported in the literature use DCT or wavelet decomposition for data embedding, the choice of the transform is not obvious.We compare the achievable data-hiding capacities for different decompositions like DCT, DFT, Hadamard, and subband transforms and show that the magnitude DFT decomposition performs best among the ones compared.

The goal of this study is to investigate the performance of the watermarking scheme proposed by Ramkumar and Akansu (see IEEE Trans. on Multimedia, 1999) for watermarked images distorted by geometrical attacks such as StirMark. Although the geometric distortions are not visually noticeable, the watermark cannot be detected due to the resulting high mean square error between the original and attacked images. In order to extract the watermark from distorted images, the effects of these attacks must be minimized. This work focuses on the recovery of an attacked image using a reliable distortion estimation. The performance test is studied for several images attacked by StirMark. The proposed algorithm is shown to reduce false alarm probability in detection of the watermark from about 0.005 for (for StirMarked images) to less than 10/sup -50/.

This paper addresses good choices for the signaling method for multimedia steganography, or data hiding. A novel FFT based signaling method, with many properties that make it especially suitable for steganographic applications is proposed. The use of FFT permits large codebook sizes, without drastically increasing the computational complexity.

Conventional spread spectrum communication methods essentially map a discrete symbol from an alphabet to a length-N real valued sequence, which represents a point in the N-dimensional signal constellation. The real valued sequence is in turn transmitted over a communications channel. However, communication schemes for the purpose of multimedia steganography (or data hiding) have to transmit the real valued sequence corresponding to a point in the signal constellation superimposed on the original or cover content (without affecting the fidelity of the original content noticeably). The detector therefore, has to estimate the origin of the signal constellation, and thereafter proceed to decode the transmitted symbol. In this paper, we explore some efficient solutions for signaling methods employing floating signal constellations.

A robust watermarking scheme for images is proposed. The proposed method can be also be easily extended to other signals like audio and video. In the proposed method an optimal solution is obtained for maximizing the detection statistic (which is an indication of the degree of certainty with which the signature or the watermark is detected), for a given permitted distortion of the host signal, and additive noise variance. Other issues for improving the security of the watermarking scheme, like key based transforms, are also addressed.

We present an information-theoretic approach to obtain an estimate of the number of bits that can be hidden in compressed image sequences. We show how addition of the message signal in a suitable transform domain rather than the spatial domain can significantly increase the data hiding capacity. We compare the data hiding capacities achievable with different block transforms and show that the choice of the transform should depend on the robustness needed. While it is better to choose transforms with good energy compaction property (like DCT, wavelet etc.) when the robustness required is low, transforms with poorer energy compaction property (like the Hadamard or Hartley transform) are preferable choices for higher robustness requirements.

We present a data hiding scheme for still images, in which only the magnitude of the DFT coefficients are altered to embed the hidden information bits. We begin by identifying various components of a typical data hiding scheme, like the decomposition used, signature design, self-noise suppression and signaling. The final choice of components for the proposed data hiding scheme are well tailored by utilizing theoretical reasonings and experimental observations. Performance results show good robustness of the data hiding scheme for both JPEG and SPIHT image compression.

We present an information-theoretic approach to obtain an estimate of the number of bits that can be hidden in still images, or, the capacity of the data-hiding channel. We show how addition of the message signal in a suitable transform domain rather than the spatial domain can significantly increase the channel capacity. We compare the capacities achievable with different decompositions like DCT, DFT, Hadamard, and subband transforms.