16218783
Complete Lax Logical Relations for Cryptographic Lambda-Calculi
Security properties are profitably expressed using notions of contextual equivalence, and logical relations are a powerful proof technique to establish contextual equivalence in typed lambda calculi, see e.g. Sumii and Pierce’s logical relation for a cryptographic lambda-calculus. We clarify Sumii and Pierce’s approach, showing that the right tool is prelogical relations, or lax logical relations in general: relations should be lax at encryption types, notably. To explore the difficult aspect of fresh name creation, we use Moggi’s monadic lambda-calculus with constants for cryptographic primitives, and Stark’s name creation monad. We define logical relations which are lax at encryption and function types but strict (non-lax) at various other types, and show that they are sound and complete for contextual equivalence at all types.
27426921
Cryptographic logical relations
Using contextual equivalence (a.k.a. observational equivalence) to specify security properties is an important idea in the field of formal verification of cryptographic protocols. While contextual equivalence is difficult to prove directly, one is usually able to deduce it using the so-called logical relations in typed @l-calculi. We apply this technique to the cryptographic metalanguage-an extension of Moggi's computational @l-calculus, where we use Stark's model for name creation to explore the difficult aspect of dynamic key generation. The categorical construction of logical relations for monadic types (by Goubault-Larrecq et al.) then allows us to derive logical relations over the category Set^I. Although Set^I is a perfectly adequate model of dynamic key generation, it lacks in some aspects when we study relations between programs in the metalanguage. This leads us to an interesting exploration of what should be the proper category to consider. We show that, to define logical relations in the cryptographic metalanguage, a better choice of category is Set^I^^^-> that we proposed in [Y. Zhang, D. Nowak, Logical relations for dynamic name creation, in: Proceedings of the 17th International Workshop of Computer Science Logic and the 8th Kurt Godel Colloqium, CSL & KGL, in: Lecture Notes in Computer Science, vol. 2803, Springer-Verlag, 2003, pp. 575-588]. However, this category is still lacking in some subtler aspects and we propose a refined category Set^P^I^^^-> to fix the flaws, but our final choice is Set^I^x^I, which is equivalent to Set^P^I^^^->. We define the contextual equivalence based on Set^I^x^I and show that the cryptographic logical relation derived over Set^I^x^I is sound and can be used to verify protocols in practice.
21919804
Logical Relations for Dynamic Name Creation
Pitts and Stark’s nu-calculus is a typed lambda-calculus which forms a basis for the study of interaction between higher-order functions and dynamically created names. A similar approach has received renewed attention recently through Sumii and Pierce’s cryptographic lambda-calculus, which deals with security protocols. Logical relations are a powerful tool to prove properties of such a calculus, notably observational equivalence. While Pitts and Stark construct a logical relation for the nu-calculus, it rests heavily on operational aspects of the calculus and is hard to be extended. We propose an alternative Kripke logical relation for the nu-calculus, which is derived naturally from the categorical model of the nu-calculus and the general notion of Kripke logical relation. This is also related to the Kripke logical relation for the name creation monad by Goubault-Larrecq et al. (CSL’2002), which the authors claimed had similarities with Pitts and Stark’s logical relation. We show that their Kripke logical relation for names is strictly weaker than Pitts and Stark’s. We also show that our Kripke logical relation, which extends the definition of Goubault-Larrecq et al., is equivalent to Pitts and Stark’s up to first-order types; our definition rests on purely semantic constituents, and dispenses with the detours through operational semantics that Pitts and Stark use.
1171092
On Completeness of Logical Relations for Monadic Types
Software security can be ensured by specifying and verifying security properties of software using formal methods with strong theoretical bases. In particular, programs can be modeled in the framework of lambda-calculi, and interesting properties can be expressed formally by contextual equivalence (a.k.a. observational equivalence). Furthermore, imperative features, which exist in most real-life software, can be nicely expressed in the so-called computational lambda-calculus. Contextual equivalence is difficult to prove directly, but we can often use logical relations as a tool to establish it in lambda-calculi. We have already defined logical relations for the computational lambda-calculus in previous work. We devote this paper to the study of their completeness w.r.t. contextual equivalence in the computational lambda-calculus.
35901095
The Computational SLR: A Logic for Reasoning about Computational Indistinguishability
Computational indistinguishability is a notion in complexity-theoretic cryptography and is used to define many security criteria. However, in traditional cryptography, proving computational indistinguishability is usually informal and becomes error-prone when cryptographic constructions are complex. This paper presents a formal proof system based on an extension of Hofmann's SLR language, which can capture probabilistic polynomial-time computations through typing and is sufficient for expressing cryptographic constructions. We in particular define rules that justify directly the computational indistinguishability between programs and prove that these rules are sound with respect to the set-theoretic semantics, hence the standard definition of security. We also show that it is applicable in cryptography by verifying, in our proof system, Goldreich and Micali's construction of pseudorandom generator.
8269275
Web Services Based State of the Environment Reporting
The Environmental Sciences Division within Queensland Environmental Protection Agency works to monitor, assess and model the condition of the environment. The Division has as a legislative responsibility to produce a whole-of-government report every four years dealing environmental conditions and trends in a ”State of the Environment report” (SoE)[1][2][3]. State of Environment Web Service Reporting System is a supplementary web service based SoE reporting tool, which aims to deliver accurate, timely and accessible information on the condition of the environment through web services via Internet [4][5]. This prototype provides a scientific assessment of environmental conditions for a set of environmental indicators. It contains text descriptions and tables, charts and maps with spatiotemporal dimensions to show the impact of certain environmental indicators on our environment. This prototype is a template based indicator system, to which the administrator may add new sql queries for new indicator services without changing the architecture and codes of this template. The benefits are brought through a service-oriented architecture which provides an online query service with seamless integration. In addition, since it uses web service architecture, each individual component within the application can be implemented by using different programming languages and in different operating systems. Although the services showed in this demo are built upon two datasets of regional ecosystem and protection area of Queensland, it will be possible to report on the condition of water, air, land, coastal zones, energy resources, biodiversity, human settlements and natural culture heritage on the fly as well. Figure 1 shows the architecture of the prototype. In the next section, I will discuss the research tasks in the prototype.
4868693
An efficient texture generation technique for human head cloning and morphing
This paper presents a technique to efficiently generate a parameterized full-head texture from a single face image of the scanned data for modeling photorealistic 3D heads. We automatically register face scans in a database by deforming a generic head mesh to fit the specific person’s face geometry with a volume morphing approach. After the face texture is transferred onto it, the 3D generic mesh is parameterized over a 2D texture domain to establish a correspondence between all the scanned textures. After having performed a vertex-toimage binding for all vertices of the head mesh, we automatically generate a full-head texture using color interpolation for unbound regions and weighted average splines for visual boundary removal. We also use a deformation method to extract ear textures from the input image for texturing individual ears. With the exception of the initial feature point selection, our method is fully automated. We show photorealistic and real-time head rendering and morphing with the resulting texture.
4002740
Selectivity Estimation by Batch-Query based Histogram and Parametric Method
Histograms are used extensively for selectivity estimation and approximate query processing. Workload-aware dynamic histograms can self-tune itself based on query feedback without scanning or sampling the underlaying datasets in a systematic and comprehensive way. Dynamic histograms allocate more buckets not only for the areas with most skewed data distribution but also according to users' interest. However, it takes long time to 'warm-up' (i.e., a large number of queries need to be processed before the histogram can provide a satisfactory coverage and accuracy). Thus, it is less effective to adapt with workload pattern changes. In this paper, we propose a novel online query scheduling algorithm which can significantly reduce the warm-up time for dynamic histograms. A parametric method is proposed to remedy the problem of inaccurate query selectivity estimation for the areas with poor histogram coverage. Experimental results demonstrate a significant effectiveness and accuracy improvement of our approach.
18837154
Inverting sensor networks and actuating the environment for spatio-temporal access control
Wireless sensor networks are typically deployed to measure the information field, rather than create an information field. However, by utilizing the radio on sensor nodes, it is possible to invert the role of sensor networks, and allow sensor nodes to actuate the environment. Such actuation can facilitate new forms of access control that are based on whether a user is located at the right place at the right time. In this paper, we explore the challenges of supporting spatio-temporal access control, where access to an object or service is based on the user's spatio-temporal context. Specifically, we focus on supporting spatio-temporal access control through the specification of access control policies, and show how complex spatio-temporal policies can be specified using automata. We outline a challenge-response mechanism for verifying user location in a centralized spatio-temporal access control mechanism. We utilize sensor networks in an inverted fashion to support spatio-temporal access control. Sensor nodes announce keys according to a time-varying schedule, and users may access restricted files/resources only if they are in the neighborhood of the correct sensor node and witness the appropriate cryptographic key.