Cryptography – Key management – Having particular key generator
Patent
1994-09-26
1997-06-10
Gregory, Bernarr E.
Cryptography
Key management
Having particular key generator
380 2, 375200, 370447, H04L 900, H04L 12413
Patent
active
056384491
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to information networks operating by radio, that is to say having the airways as communication medium, in particular those which function in batch mode.
SUMMARY OF THE INVENTION
The applicant made initial general proposals in his French patent application no. 92 04 032 (FR-A-2 689 658; WO-93/20636). He proposed certain improvements in a subsequent French patent application no. 93 00 750, which, in accordance with a new provision of the French law, enabled the second application (93 00 750) to benefit from the filing date of the first one (92 04 032), for the joint parties. The present application concerns the new elements in application no. 93 00 750, presented in summary form.
The proposed data transmission installation is of the type comprising at least two data processing stations [postes de traitement de donnees] (the word "traitement" being understood in its most elementary sense). Each station is equipped with a network interface capable of transmitting messages on request, and of collecting messages received. This comprises an emission-reception management device. Also provided are a test means for recognizing a collision condition ("collision detector") together with a collision resolving means, following upon a recognized collision condition.
One of the main functions of this management device is to give confirmative emission and reception orders to the network interface.
According to the previous application FR 92 04 032, each of the stations comprises a pluridirectional radio emission-reception device (involving several directions, but not necessarily omnidirectional). In its modes of execution described in detail, it is provided in particular that this radio emission-reception device operates on a central channel, as well as on one or more lateral channels.
It was found that these first proposals could present disadvantages, particularly because of congestion of the airways.
The aim of the present application is to provide a solution to this problem.
The invention is based on a network where at least two data processing stations are provided, each equipped with a network interface. These stations are capable of cooperating by radio in a chosen frequency band, or data channel, to emit messages on request and to collect messages received. The stations to this end establish confirmative emission or reception orders.
According to a characteristic of the invention, in response to an order confirming emission of a message in a station, there is carried out in said frequency band (used for the data) rapidly alternating emission/reception, according to a chosen pattern peculiar to this station. A collision is recognized if a signal higher in strength than an initial threshold strength is received for a substantial part of at least one silence of this rapid alternating emission/reception, thus demonstrating the concomitant emission of another station.
In equipment terms, each of the stations comprises a radio emission-reception device operating in a chosen frequency band, where it is capable of rapid emission-reception switching. In response to an order confirming emission of a message or a batch, said device operates in rapidly alternating emission-reception mode, according to a pattern chosen to be peculiar to this emission/reception device. A collision is recognised by a collision detecting means if a signal higher in strength than an initial threshold strength is received during a substantial part of at least one silence of this rapid alternating emission/reception, thus demonstrating the concomitant emission of another station.
In the presence of a recognized collision, if data of the message have already been transmitted, their transmission can be invalidated; it is decided, if necessary, not to transmit the remainder of the message or batch; and a collision processing procedure is undertaken in certain cases, particular if collision resolution is necessary.
In the absence of recognized collision, the emission of a part at least of any remainde
REFERENCES:
patent: 4641375 (1987-02-01), Dean
patent: 4665519 (1987-05-01), Kirchner et al.
patent: 5040175 (1991-08-01), Tuch et al.
Yamauchi, "Reliable Multicast Over The Mobile Packet Radio Channel", IEEE hicular Technology Conference, pp. 366-371, (1990).
Jacquet Philippe
Muhlethaler Paul
Gregory Bernarr E.
INRIA Institut National de Recherche en Informatique et en Autom
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