Systeme d'authentification analogique reciproque entre un terminal et une ligne de transmission
First Claim
Patent Images
1. A system for authenticating a call by analog frequency signals lying in a first or data range of frequencies between a transmitter/receiver terminal and a communications line, the system being characterized in that it further includes a monitoring device connected in said line, and in that:
- said terminal includes means for generating authentication frequency signals in addition to said communications signals with a periodicity T while a call is in progress, said authentication signals having frequencies lying in a second frequency range, said authentication signals comprising, for each period, a fixed first signal f1i characteristic of said terminal, and a variable second signal f2i ;
said terminal and said monitoring device each including means for interchanging a first common value K1 in the form of frequencies prior to a call being set up, means for implementing a common algorithm for generating respective second frequency values f2i and f'"'"'2i at each period T and depending at least on the preceding second frequency value, respectively f2i-1 and f'"'"'2i-1 ;
said terminal further including means for emitting said frequencies f1i and f2i at each period; and
said monitoring device further including means for comparing each first frequency f1i with predetermined first frequency values, and for comparing each received second frequency f2i with the corresponding calculated second frequency f'"'"'2i, over a predetermined approximation range corresponding to line transmission, and means for inhibiting said call as a function of the results of said comparisons.
1 Assignment
0 Petitions
Accused Products
Abstract
The invention relates to a system for mutual authentication between a transmission line and a terminal, e.g. a prepayment telephone set.
The telephone (2) is connected to the line (14) via a monitoring device (18). Electronic circuits (18) and (12) are associated with the monitoring device and with the telephone in order to generate authentication frequency signals throughout the call at inaudible frequencies.
35 Citations
21 Claims
-
1. A system for authenticating a call by analog frequency signals lying in a first or data range of frequencies between a transmitter/receiver terminal and a communications line, the system being characterized in that it further includes a monitoring device connected in said line, and in that:
-
said terminal includes means for generating authentication frequency signals in addition to said communications signals with a periodicity T while a call is in progress, said authentication signals having frequencies lying in a second frequency range, said authentication signals comprising, for each period, a fixed first signal f1i characteristic of said terminal, and a variable second signal f2i ; said terminal and said monitoring device each including means for interchanging a first common value K1 in the form of frequencies prior to a call being set up, means for implementing a common algorithm for generating respective second frequency values f2i and f'"'"'2i at each period T and depending at least on the preceding second frequency value, respectively f2i-1 and f'"'"'2i-1 ; said terminal further including means for emitting said frequencies f1i and f2i at each period; and said monitoring device further including means for comparing each first frequency f1i with predetermined first frequency values, and for comparing each received second frequency f2i with the corresponding calculated second frequency f'"'"'2i, over a predetermined approximation range corresponding to line transmission, and means for inhibiting said call as a function of the results of said comparisons. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
-
Specification
-
- Resources
Litigation Campaign Assessment
Thank you for your request. You will receive a custom alert email when the Litigation Campaign Assessment is available.
×
-
Current AssigneeSchlumberger Industries Incorporated (Schlumberger NV)
-
Original AssigneeSchlumberger Industries Incorporated (Schlumberger NV)
-
InventorsBarraud, Claude
-
Primary Examiner(s)Schreyer, Stafford D.
-
Application NumberUS07/181,605Time in Patent Office467 DaysField of Search379/27, 379/145, 379/155, 379/154, 379/189, 194/202, 380/30US Class Current379/145CPC Class CodesH04K 1/00 Secret communicationH04M 1/66 with means for preventing u...H04M 17/023 Circuit arrangements
