The provable security of secure positioning in position-based cryptography was investigated,and the provable secure model of secure positioning was established in the universally composable framework.According to the security requirements of secure positioning,the ideal functionality of secure positioning firstly was proposed.Then,the ideal functionality of bounded retrieval model was designed as one of the set-up assumptions in position-based cryptography.Lastly,the secure positioning protocol in 1-dimension space,as an example,could securely realize the functionality of secure positioning in the bounded retrieval model.
The provable security of secure positioning in position-based cryptography was investigated,and the provable secure model of secure positioning was established in the universally composable framework.According to the security requirements of secure positioning,the ideal functionality of secure positioning firstly was proposed.Then,the ideal functionality of bounded retrieval model was designed as one of the set-up assumptions in position-based cryptography.Lastly,the secure positioning protocol in 1-dimension space,as an example,could securely realize the functionality of secure positioning in the bounded retrieval model.
The Universal Composability (UC) framework provides provable security guaranties for harsh application environment, where we want to construct protocols which keep security guarantees even when they are concurrently composed with arbitrary number of arbitrary (even hostile) protocols.This is a very strong guarantee.The UC-framework inherently supports the modular design, which allows secure composition of arbitrary number of UC-secure components with an arbitrary protocol.In contrast, traditional analysis and design is a stand alone analysis where security of a single instance is considered, i.e. an instance which is not in potential interaction with any concurrent instances.Furthermore, a typical traditional analysis is informal, i.e. without a formal proof.In spite of these facts, beyond the task of key-exchange this technology have not really took the attention of the community of applied cryptography.From practitioner's point of view the UC-world may seem more or less an academic interest of theoretical cryptographers.Accordingly we take a pragmatic approach, where we concentrate on meaningful compromises between the assumed adversarial strength, ideality wishes and realization complexity while keeping provable security guarantees within the UC-framework.We believe that even modest but provable goals (especially, if tunable to application scenarios) are interesting if a wider penetration of the UC-technology is desired into the daily-practice of protocol applications.
In this paper, we initiate the theoretical study of cryptographic protocols where the identity, or other credentials and inputs, of a party are derived from its geographic location. We start by considering the central task in this setting, i.e., securely verifying the position of a device. Despite much work in this area, we show that in the vanilla (or standard) model, the above task (i.e., of secure positioning) is impossible to achieve, even if we assume that the adversary is computationally bounded. In light of the above impossibility result, we then turn to Dziembowski's bounded retrieval model (a variant of Maurer's bounded storage model) and formalize and construct information theoretically secure protocols for two fundamental tasks: secure positioning and position-based key exchange. We then show that these tasks are in fact universal in this setting---we show how we can use them to realize secure multiparty computation. Our main contribution in this paper is threefold: to place the problem of secure positioning on a sound theoretical footing; to prove a strong impossibility result that simultaneously shows the insecurity of previous attempts at the problem; and to present positive results showing that the bounded-retrieval framework is a fruitful one to study the foundations of position-based cryptography.
A desirable goal for cryptographic protocols is to guarantee security when the protocol is composed with other protocol instances. Universally Composable (UC) security provides this guarantee in a strong sense: A UC-secure protocol maintains its security properties even when composed concurrently with an unbounded number of instances of arbitrary protocols. However, many interesting cryptographic tasks are provably impossible to realize with UC security in the standard, “plain” model of computation. Impossibility holds even if ideally authenticated communication channels are provided. In contrast, it has been demonstrated that general secure computation can be obtained in a number of idealized models. Each one of these models represents a form of trust that is put in some of the system’s components. This survey examines and compares some of these trust models, both from the point of view of their sufficiency for building UC secure protocols, and from the point of view of their practical realizability. We start with the common reference string (CRS) model, and then describe several relaxations and alternatives including the Defective CRS model, the key registration models, the hardware token model, the global and augmented CRS models, and a timing assumption. Finally, we briefly touch upon trust models for obtaining authenticated communication.
Abstract. This paper analyzes group communication within the universally composable framework. We first propose the group communication model, identity-based signcrytion mod-el and group key distribution model in the UC framework by designing the ideal functionality FSAGCOM, FIDSC and FGKD, respectively. Then, we construct a UC secure identity-based signcryption protocol πIDSC. Moreover, we shows that the identity-based signcryption πIDSC securely realizes the ideal functionality FIDSC if and only if the corresponding protocol ID-SC is secure. Finally, based on the identity-based protocol, we propose a group communica-tion scheme πSAGCOM, which can securely realizes the ideal functionality FSAGCOM in the (FIDSC,FGKD)-hybrid model.
The provable security of ID-based key exchange protocols was investigated. In the universally composable framework, the provable secure model of ID-based key exchange was proposed. The ability of the adversary to corrupt key generation center was added to the adversary model. According to the characteristics of ID-based key exchange, the ideal functionality of ID-based key exchange was presented. Based on the adversary model and the ideal functionality, the proposed model captures not only the universally composable security of ID-based key exchange, but also implies one of the important properties of ID-based key exchange——key generation center forward secrecy. In addition, the protocol （with key confirmation） proposed by Chen and Kudla can securely realize the functionality of ID-based KE with KGC-FS.
In this thesis, we initiate the study of cryptographic protocols where the identity, or other credentials and inputs, of a party are derived from its geographic location.
We start by considering the central task in this setting, i.e., securely verifying the position of a device. Despite much work in this area, we show that in the Vanilla (or standard) model, this above task (i.e., of secure positioning) is impossible to achieve, even if we assume that the adversary is computationally bounded. In light of the above impossibility result, we then turn to Dziembowski's Bounded Retrieval Model (a variant of Maurer's Bounded Storage Model) and formalize and construct information theoretically secure protocols for two fundamental tasks: Secure Positioning; and Position-Based Key Exchange.
We then show that these tasks are in fact universal in this setting—we show how we can use them to realize Secure Multi-Party Computation.
The main contribution of this thesis is threefold: to place the problem of secure positioning on a sound theoretical footing; to prove a strong impossibility result that simultaneously shows the insecurity of previous attempts at the problem; and to present positive results showing that the bounded-retrieval framework is a fruitful one to study the foundations of position-based cryptography.
This thesis is based on joint works with Vipul Goyal, Ryan Moriarty, and Rafail Ostrovsky.