Key Agreement with Correlated Noise and Multiple Entities or Enrollments

We extend a basic key agreement model with a hidden identifier source to a multi-user model with joint secrecy and privacy constraints over all entities that do not trust each other. Different entities that use different measurements of the same remote source through broadcast channels (BCs) to agree on mutually-independent local secret keys are considered. This model is the proper multi-user extension of the basic model since the encoder and decoder pairs are not assumed to trust other pairs, unlike assumed in the literature. Strong secrecy constraints imposed jointly on all secret keys, which is more stringent than separate secrecy leakage constraints for each secret key considered in the literature, are satisfied. Inner bounds for maximum key rate, and minimum privacy-leakage and storage rates are proposed for any finite number of entities. Inner and outer bounds for degraded and less-noisy BCs are given to illustrate cases with strong privacy. A multi-enrollment model that is used for common physical unclonable functions (PUFs) is also considered to establish inner and outer bounds for key-leakage-storage regions that differ only in the Markov chains imposed. For this special case, the encoder and decoder measurement channels have the same channel transition matrix and secrecy leakage is measured for each secret key separately. We illustrate cases for which it is useful to have multiple enrollments as compared to a single enrollment and vice versa

Key Agreement with Physical Unclonable Functions and Biometric Identifiers

This thesis addresses security and privacy problems for digital devices and biometrics, where a secret key is generated for authentication, identification, or secure computations. A physical unclonable function (PUF) is a promising solution for local security in digital devices. A low-complexity transform-coding algorithm is developed to make the information-theoretic analysis tractable and motivate a noisy (hidden) PUF source model. The optimal trade-offs between the secret-key, privacy-leakage, and storage rates for multiple measurements of hidden PUFs are characterized. The first optimal and low-complexity code constructions are proposed. Polar codes are designed to achieve the best known rate tuples. The gains from cost-constrained controllable PUF measurements are illustrated to motivate extensions

Effects of Quantization on the Multiple-Round Secret-Key Capacity

We consider the strong secret key (SK) agreement problem for the satellite communication setting, where a satellite chooses a common binary phase shift keying modulated input for three statistically independent additive white Gaussian noise measurement channels whose outputs are observed by two legitimate transceivers (Alice and Bob) and an eavesdropper (Eve), respectively. Legitimate transceivers have access to an authenticated, noiseless, two-way, and public communication link, so they can exchange multiple rounds of public messages to agree on a SK hidden from Eve. Without loss of essential generality, the noise variances for Alice\u27s and Bob\u27s measurement channels are both fixed to a value Q>1, whereas the noise over Eve\u27s measurement channel has a unit variance, so Q represents a channel quality ratio. We show that when both legitimate transceivers apply a one-bit uniform quantizer to their noisy observations before SK agreement, the SK capacity decreases at least quadratically in Q

The role of travel intermediaries in the development of sustainable mountain tourism. The case of Turkey

The aim of the study is to investigate the current situation of mountain tourism and its sustainability in Turkey as a new and ascending tourism product. In addition, tourism policies of Turkish Ministry of Culture and Tourism in the mountain tourism area are scrutinized. Not only the tourism policies of the government are enough to promote a new alternative tourism type, but also the role and effects of tourism middlemen such as travel agencies, tour operators, and tour wholesalers cannot be denied in the promotion of a destination. Mountain tourism can be accepted and classified as one of these mentioned alternative and newly developed types of tourism in many destinations. Therefore, mountain tourism could be one of the best alternative tourism opportunities for many destinations if they have sufficient resources, namely naturally attractive mountains and related infra and/or superstructure

El papel de los intermediarios de viajes en el desarrollo del turismo sostenible de montaña. El caso de Turquía

The aim of the study is to investigate the current situation of mountain tourism and its sustainability in Turkey as a new and ascending tourism product. In addition, tourism policies of Turkish Ministry of Culture and Tourism in the mountain tourism area are scrutinized. Not only the tourism policies of the government are enough to promote a new alternative tourism type, but also the role and effects of tourism middlemen such as travel agencies, tour operators, and tour wholesalers cannot be denied in the promotion of a destination. Mountain tourism can be accepted and classifi ed as one of these mentioned alternative and newly developed types of tourism in many destinations. Therefore, mountain tourism could be one of the best alternative tourism opportunities for many destinations if they have suffi cient resources, namely naturally attractive mountains and related infra and/or superstructure.El objetivo de este estudio es investigar la situación actual del turismo de montaña y su sostenibilidad en Turquía como un nuevo y ascendente producto turístico. Además, las políticas turísticas del Ministerio turco de Cultura y Turismo en el área de turismo de montaña son objeto de revisión. En la promoción del nuevos tipos de turismo alternativo no sólo se encuentra implicada la política turística desarrollada por el gobierno, sino que infl uyen sobremanera el papel y los efectos de los intermediarios turísticos, tales como agencias de viajes, operadores y mayoristas turísticos que promueven un destino. El turismo de montaña puede ser aceptado y se clasifica como una de estas alternativas a los productos más convencionales y se inserta en los tipos de reciente desarrollo en muchos destinos. Por lo tanto, el turismo de montaña podría ser una de las mejores oportunidades de turismo alternativo para muchos destinos si tienen los recursos suficientes, las montañas como atractivos naturales y condiciones infra y superestructurales

Multiple Noisy Private Remote Source Observations for Secure Function Computation

The problem of reliable function computation is extended by imposing privacy, secrecy, and storage constraints on a remote source whose noisy measurements are observed by multiple parties. The main additions to the classic function computation problem include 1) privacy leakage to an eavesdropper is measured with respect to the remote source rather than the transmitting terminals\u27 observed sequences; 2) the information leakage to a fusion center with respect to the remote source is considered as another privacy leakage metric; 3) two transmitting node observations are used to compute a function. Inner and outer bounds on the rate regions are derived for lossless single-function computation with two transmitting nodes, which recover previous results in the literature, and for special cases that consider invertible functions simplified bounds are established

Secure Lossy Function Computation with Multiple Private Remote Source Observations

We consider that multiple noisy observations of a remote source are used by different nodes in the same network to compute a function of the noisy observations under joint secrecy, joint privacy, and individual storage constraints, as well as a distortion constraint on the function computed. Suppose that an eavesdropper has access to one of the noisy observations in addition to the public messages exchanged between legitimate nodes. This model extends previous models by 1) considering a remote source as the source of dependency between the correlated random variables observed at different nodes; 2) allowing the function computed to be a distorted version of the target function, which allows to reduce the storage rate as compared to a reliable function computation scenario in addition to reducing secrecy and privacy leakages; 3) introducing a privacy metric that measures the information leakage about the remote source to the fusion center in addition to the classic privacy metric that measures the leakage to an eavesdropper; 4) considering two transmitting nodes to compute a function rather than one node. Single-letter inner and outer bounds are provided for the considered lossy function computation problem, and simplified bounds are established for two special cases, in which either the computed function is partially invertible or the function is invertible and the measurement channel of the eavesdropper is physically degraded with respect to the measurement channel of the fusion center

Private Remote Sources for Secure Multi-Function Computation

We consider a distributed function computation problem in which parties observing noisy versions of a remote source facilitate the computation of a function of their observations at a fusion center through public communication. The distributed function computation is subject to constraints, including not only reliability and storage but also secrecy and privacy. Specifically, 1) the function computed should remain secret from an eavesdropper observing the public communication and correlated observations, measured in terms of the information leaked about the arguments of the function, to ensure secrecy regardless of the exact function used; 2) the remote source should remain private from the eavesdropper and the fusion center, measured in terms of the information leaked about the remote source itself. We derive the exact rate regions for lossless and lossy single-function computation and illustrate the lossy single-function computation rate region for an information bottleneck example, in which the optimal auxiliary random variables are characterized for binary-input symmetric-output channels. We extend the approach to lossless and lossy asynchronous multiple-function computations with joint secrecy and privacy constraints, in which case inner and outer bounds for the rate regions that differ only in the Markov chain conditions imposed are characterized

Federated Learning with Local Differential Privacy: Trade-offs between Privacy, Utility, and Communication

Federated learning (FL) allows to train a massive amount of data privately due to its decentralized structure. Stochastic gradient descent (SGD) is commonly used for FL due to its good empirical performance, but sensitive user information can still be inferred from weight updates shared during FL iterations. We consider Gaussian mechanisms to preserve local differential privacy (LDP) of user data in the FL model with SGD. The trade-offs between user privacy, global utility, and transmission rate are proved by defining appropriate metrics for FL with LDP. Compared to existing results, the query sensitivity used in LDP is defined as a variable and a tighter privacy accounting method is applied. The proposed utility bound allows heterogeneous parameters over all users. Our bounds characterize how much utility decreases and transmission rate increases if a stronger privacy regime is targeted. Furthermore, given a target privacy level, our results guarantee a significantly larger utility and a smaller transmission rate as compared to existing privacy accounting methods

Secure Integrated Sensing and Communication

This work considers the problem of mitigating information leakage between communication and sensing in systems jointly performing both operations. Specifically, a discrete memoryless state-dependent broadcast channel model is studied in which (i) the presence of feedback enables a transmitter to convey information, while simultaneously performing channel state estimation; (ii) one of the receivers is treated as an eavesdropper whose state should be estimated but which should remain oblivious to part of the transmitted information. The model abstracts the challenges behind security for joint communication and sensing if one views the channel state as a sensitive attribute, e.g., location. For independent and identically distributed states, perfect output feedback, and when part of the transmitted message should be kept secret, a partial characterization of the secrecy-distortion region is developed. The characterization is exact when the broadcast channel is either physically-degraded or reversely-physically-degraded. The partial characterization is also extended to the situation in which the entire transmitted message should be kept secret. The benefits of a joint approach compared to separation-based secure communication and state-sensing methods are illustrated with binary joint communication and sensing models