2 resultados para Ambiguity resolution

em Deakin Research Online - Australia


Relevância:

40.00% 40.00%

Publicador:

Resumo:

Optimistic fair exchange (OFE) allows two parties to exchange their digital items in a fair way. As one of the fundamental problems in secure electronic business and digital rights management, OFE has been studied intensively since its introduction. This paper introduces and defines a new property for OFE: Strong Resolution-Ambiguity. We show that many existing OFE protocols have the new property, but its formal investigation has been missing in those protocols. We prove that in the certified-key model, an OFE protocol is secure in the multi-user setting if it is secure in the single-user setting and has the property of strong resolution-ambiguity. Our result not only simplifies the security analysis of OFE protocols in the multi-user setting but also provides a new approach for the design of multi-user secure OFE protocols. Following this approach, a new OFE protocol with strong resolution-ambiguity is proposed. Our analysis shows that the protocol is setup-free, stand-alone and multi-user secure without random oracles.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The adjoining area of western Guizhou and eastern Yunnan Provinces in southwest China is an ideal place to investigate the feasibility of correlating marine and nonmarine Permian–Triassic boundary (PTB) sequences, as it contains outcrop sections of shallow marine, marginal marine (or paralic), and terrestrial PTB sections, all in close geographic proximity. This paper documents for the first time multiple stratigraphic data from several well-preserved terrestrial PTB sections in the area and attempts to use these data to define, locate, and correlate the PTB in the area. A study of the spores and pollen and vegetation types across the terrestrial PTB sections in the study area suggests three distinct evolutionary stages across the boundary: Stage 1 (Xuanwei Formation) is characterised by Late Permian or Paleozoic-type ferns and pteridosperms (85.0%), with a few gymnosperms (15.0%); stage 2 is marked by an abrupt drop of sporopollen elements of Late Permian aspects, coupled with the appearance of fungal spores and limited Early Triassic palynomorphs; stage 3 (top Xuanwei Formation and Kayitou Formation) is dominated by gymnosperm pollen (58.8%) of clearly Early Triassic aspect, although still retaining limited ferns and pteridosperms. The three biotic stages seem to well correspond with the changing trend of the δ13Corg curves from the same sections, which is characterized by a sharp drop just before the PTB, followed by a short term partial recovery across the boundary, and then succeeded by a gradual decline after the PTB in the Early Triassic. Combining evidence from eventostratigraphic (i.e., the succession of boundary clay beds), biostratigraphic (using both macroplants and palynomorphs), and chemostratigraphic (i.e., organic carbon isotope excursion signals), we propose that a high-resolution PTB succession, closely correlatable to its marine counterpart at the Meishan section in eastern China, is recognisable at the terrestrial PTB sections in the western Guizhou–eastern Yunnan area in southwest China.