We first consider the construction with two different primitives: one for intermediate calls and another for finalization. In this paper, we study the security of PMAC-type constructions generalizing the underlying primitive to keyed functions. With our approach we aim to preserve the advantages of RBAC, and o#er an additional means for the definition and enforcement of fine-grained context-dependent access control policies. We present an engineering process for context constraints, that is based on goal-oriented requirements engineering techniques, and describe how we extended the design and implementation of an existing RBAC service to enable the enforcement of context constraints. Accordingly, a conditional permission is an RBAC permission which is constrained by one or more context constraints. If these conditions are satisfied, the corresponding access request can be permitted. In our approach a context constraint is defined as a dynamic RBAC constraint that checks the actual values of one or more contextual attributes for predefined conditions. This paper presents an approach that uses special purpose RBAC constraints to base certain access control decisions on context information. Plugging in known constructions of functional encryption schemes, we obtain function-private schemes based either on the Learning with Errors assumption, on obfuscation assumptions, on simple multilinear-maps assumptions, and even on the existence of any one-way function (offering various trade-offs between security and efficiency). Our transformation preserves the message privacy of the underlying scheme, and can be instantiated using a variety of existing schemes. We present a generic transformation that yields a function-private functional encryption scheme, starting with any non-function-private scheme for a sufficiently rich function class. Despite its great potential, the known function-private private-key schemes either support rather limited families of functions (such as inner products), or offer somewhat weak notions of function privacy. , reveal essentially no information other than the values i,j ∈. Together with decryption keys corresponding to functions f1, …, fT Specifically, one can hope to construct schemes where encryptions of messages m1, …, mT privacy is inherently limited in the public-key setting, in the private-key setting it has a tremendous potential. Although the vast majority of research on functional encryption has so far focused on the privacy of the encrypted messages, in many realistic scenarios it is crucial to offer privacy also for the functions for which decryption keys are provided. The spectral calculations from the molecular dynamics simulations reproduce the experimental findings this allows us to interpret our experimental findings in terms of a stepwise change from one to two molten bilayers at the transition temperature.Ĭrystalline ice stepwise sum frequency generation surface melting water.Functional encryption supports restricted decryption keys that allow users to learn specific functions of the encrypted messages. For the basal face, a stepwise, sudden weakening of the hydrogen-bonded structure of the outermost water layers occurs at 257 K. Using SFG, we probe the outermost water layers of distinct single crystalline ice faces at different temperatures. To elucidate the precise temperature variation of the QLL, and its nature, we investigate the surface melting of hexagonal ice by combining noncontact, surface-specific vibrational sum frequency generation (SFG) spectroscopy and spectra calculated from molecular dynamics simulations. Approaching the bulk melting temperature from below, the thickness of the QLL is known to increase. On the surface of water ice, a quasi-liquid layer (QLL) has been extensively reported at temperatures below its bulk melting point at 273 K.
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