Hadi Ahmadi

The Formal Design Model of a Lift Dispatching System (LDS)

A Lift Dispatching System (LDS) is a typical real-time system that is highly complicated in design and implementation. This article presents the formal design, specification, and modeling of the LDS system using a denotational mathematics known as Real-Time Process Algebra (RTPA). The conceptual model of the LDS system is introduced as the initial requirements for the system. The architectural model of the LDS system is created using RTPA architectural modeling methodologies and refined by a set of Unified Data Models (UDMs). The static behaviors of the LDS system are specified and refined by a set of Unified Process Models (UPMs) for the lift dispatching and serving processes. The dynamic behaviors of the LDS system are specified and refined by process priority allocation and process deployment models. Based on the formal design models of the LDS system, code can be automatically generated using the RTPA Code Generator (RTPA-CG), or be seamlessly transferred into programs by programmers. The formal models of LDS may not only serve as a formal design paradigm of real-time software systems, but also a test bench of the expressive power and modeling capability of exiting formal methods in software engineering. SPE cial SE ction

Secret keys from channel noise

We study the problem of unconditionally secure Secret Key Establishment (SKE) when Alice and Bob are connected by two noisy channels that are eavesdropped by Eve. We consider the case that Alice and Bob do not have any sources of initial randomness at their disposal. We start by discussing special cases of interest where SKE is impossible and then provide a simple SKE construction over binary symmetric channels that achieves some rates of secret key. We next focus on the Secret Key (SK) capacity and provide lower and upper bounds on this capacity. We prove the lower bound by proposing a multi-round SKE protocol, called the main protocol. The main protocol consists of an initialization round and the repetition of a two-round SKE sub-protocol, called the basic protocol. We show that the two bounds coincide when channels do not leak information to the adversary. We apply the results to the case that communicants are connected by binary symmetric channels.

Secret key establishment over a pair of independent broadcast channels

We consider the problem of secret key establishment (SKE) in the presence of a passive adversary, Eve, when Alice and Bob are connected by a pair of independent discrete memoryless broadcast channels in opposite directions. We refer to this setup as 2DMBC. We define the secret-key capacity in this setup and provide a lower bound on the capacity by proposing a two-round SKE protocol. We also prove an upper bound and show that the two bounds coincide in the case of degraded 2DMBCs.

Detection of Algebraic Manipulation in the Presence of Leakage

We investigate the problem of algebraic manipulation detection (AMD) over a communication channel that partially leaks information to an adversary. We assume the adversary is computationally unbounded and there is no shared key or correlated randomness between the sender and the receiver. We introduce leakage-resilient (LR)-AMD codes to detect algebraic manipulation in this model.

Systematic profitability analysis of binary network marketing organizations

Purpose – This paper seeks to introduce a systematic approach to simulating a given binary network marketing (NM) growth topology in a definite society of people.Design/methodology/approach – The study represented a binary plan network by its binary rooted tree, where each node represents a down‐line distributor of the root. The paper sought to find a cost function which would identify which existing node is most eligible to attract the new node. Using a survey strategy, the paper introduced some effective criteria, where cost function and design systematic algorithms were introduced, in order to simulate an NM growth topology. According to the designed algorithms, the paper modified a currently used compensation plan of the Questnet Company.Findings – The comparison results indicate that the modified plan improves the efficiency by 6 percent, in the sense of profitability for the costumers, and also penetrates the market in 80 percent of trials.Research limitations/implications – The paper did not find a...

Distance Lower Bounding

Distance upper-bounding DUB allows a verifier to know whether a proving party is located within a certain distance bound. DUB protocols have many applications in secure authentication and location based services. We consider the dual problem of distance lower bounding DLB, where the prover proves it is outside a distance bound to the verifier. We motivate this problem through a number of application scenarios, and model security against distance fraud DF, Man-in-the-Middle MiM, and collusion fraud CF attacks. We prove impossibility of security against these attacks without making physical assumptions. We propose approaches to the construction of secure protocols under reasonable assumptions, and give detailed design of our DLB protocol and prove its security using the above model. This is the first treatment of the DLB problem in the untrusted prover setting, with a number of applications and raising new research questions. We discuss our results and propose directions for future research.

Common randomness and secret key capacities of two-way channels

Common Randomness Generation (CRG) and Secret Key Establishment (SKE) are fundamental primitives in information theory and cryptography. We study these two problems over the two-way communication channel model, introduced by Shannon. In this model, the common randomness (CK) capacity is defined as the maximum number of random bits per channel use that the two parties can generate. The secret key (SK) capacity is defined similarly when the random bits are also required to be secure against a passive adversary. We provide lower bounds on the two capacities. These lower bounds are tighter than those one might derive based on the previously known results. We prove our lower bounds by proposing a two-round, two-level coding construction over the two-way channel. We show that the lower bound on the common randomness capacity can also be achieved using a simple interactive channel coding (ICC) method. We furthermore provide upper bounds on these capacities and show that the lower and the upper bounds coincide when the two-way channel consists of two independent (physically degraded) one-way channels. We apply the results to the case where the channels are binary symmetric.

Private Message Transmission Using Disjoint Paths

We consider private message transmission (PMT) between two communicants, Alice and Bob, in the presence of an eavesdropper, Eve. Alice and Bob have no shared keys and Eve is computationally unbounded. There is a total of n communicating paths, but not all may be simultaneously accessible to the parties. We let t a , t b , and t e denote the number of paths that are accessible to Alice, Bob and Eve respectively. We allow the parties to change their accessed paths at certain points in time during the PMT protocol. We study perfect (P)-PMT protocol families that guarantee absolute privacy and reliability of message transmission. For the sake of transmission rate improvement, we also investigate asymptotically-perfect (AP)-PMT protocol families that provide negligible error and leakage and behave the same as P-PMT families when message length tends to infinity.

Message transmission and key establishment: General equality for weak and strong capacities

Abstract Secure communication using noisy resources has been first studied in the contexts of secure message transmission (SMT) by Wyner as well as Csiszar-and-Korner, and secret key establishment (SKE) by Ahlswede-and-Csiszar as well as Maurer. The work defines secrecy (resp. secret-key (SK)) capacity as the highest achievable rate of secure transmission (resp. key establishment). Focusing on SKE, Maurer and Wolf later noticed that the secrecy requirement in the SKE study was weak as it required only the “ratio” between the adversarys information and the key length to be negligible. They suggested a stronger definition of the SK capacity by requiring absolute information leakage to be negligible. They provided an interesting proof for the equality of weak and strong SK capacities in the above scenarios (setups). Followup work has since studied SKE in various setups considering the weak SK capacity without discussing whether the results also hold for the strong definition. In this paper, we pose the question whether the equality of weak and strong SK capacities can be derived in general for all setups with discrete memoryless resources. We first extract the requirements that have been implicit in Maurer-and-Wolfs proof and then investigate whether these required conditions can be removed. Our results show that weak and strong SK capacities are equal for any discrete memoryless communication setup. We also extend this study to message transmission and prove the equality of weak and strong secrecy capacities in any discrete memoryless setup.

New results on Secret Key Establishment over a pair of broadcast channels

Secret Key Establishment (SKE) over a pair of independent Discrete Memoryless Broadcast Channels (DMBCs) was studied in [3] where lower and upper bounds on the secret-key capacity were provided. In this paper, we study the above setup for two cases: (1) the DMBCs have “secrecy potential”, and (2) the DMBCs are stochastically degraded with independent channels. For (1), we propose a simple SKE protocol using the novel Interactive Channel Coding (ICC) method and prove that it achieves the lower bound. For (2), we give a simplified expression for the lower bound and prove that, when one of the legitimate parties sends only i.i.d. variables, the lower bound is tight and the capacity is achieved by a two-round protocol.