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Title: Secure distance ranging by electronic means

Abstract

A system for secure distance ranging between a reader 11 and a tag 12 wherein the distance between the two is determined by the time it takes to propagate a signal from the reader to the tag and for a responsive signal to return, and in which such time is random and unpredictable, except to the reader, even though the distance between the reader and tag remains the same. A random number (19) is sent from the reader and encrypted (26) by the tag into a number having 16 segments of 4 bits each (28). A first tag signal (31) is sent after such encryption. In response, a random width start pulse (13) is generated by the reader. When received in the tag, the width of the start pulse is measured (41) in the tag and a segment of the encrypted number is selected (42) in accordance with such width. A second tag pulse is generated at a time T after the start pulse arrives at the tag, the time T being dependent on the length of a variable time delay t.sub.v which is determined by the value of the bits in the selected segment of the encrypted number. Atmore » the reader, the total time from the beginning of the start pulse to the receipt of the second tag signal is measured (36, 37). The value of t.sub.v (21, 22, 23, 34) is known at the reader and the time T is subtracted (46) from the total time to find the actual propagation t.sub.p for signals to travel between the reader 11 and tag 12. The propagation time is then converted into distance (46).« less

Inventors:
 [1]
  1. Pleasanton, CA
Issue Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
OSTI Identifier:
868371
Patent Number(s):
5126746
Assignee:
United States of America as represented by United States (Washington, DC)
Patent Classifications (CPCs):
G - PHYSICS G01 - MEASURING G01S - RADIO DIRECTION-FINDING
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
secure; distance; ranging; electronic; means; reader; 11; tag; 12; determined; time; takes; propagate; signal; responsive; return; random; unpredictable; remains; 19; encrypted; 26; 16; segments; bits; 28; 31; encryption; response; width; start; pulse; 13; generated; received; measured; 41; segment; selected; 42; accordance; arrives; dependent; length; variable; delay; value; total; beginning; receipt; 36; 37; 21; 22; 23; 34; subtracted; 46; propagation; signals; travel; converted; time delay; electronic means; secure distance; distance ranging; /342/

Citation Formats

Gritton, Dale G. Secure distance ranging by electronic means. United States: N. p., 1992. Web.
Gritton, Dale G. Secure distance ranging by electronic means. United States.
Gritton, Dale G. Wed . "Secure distance ranging by electronic means". United States. https://www.osti.gov/servlets/purl/868371.
@article{osti_868371,
title = {Secure distance ranging by electronic means},
author = {Gritton, Dale G},
abstractNote = {A system for secure distance ranging between a reader 11 and a tag 12 wherein the distance between the two is determined by the time it takes to propagate a signal from the reader to the tag and for a responsive signal to return, and in which such time is random and unpredictable, except to the reader, even though the distance between the reader and tag remains the same. A random number (19) is sent from the reader and encrypted (26) by the tag into a number having 16 segments of 4 bits each (28). A first tag signal (31) is sent after such encryption. In response, a random width start pulse (13) is generated by the reader. When received in the tag, the width of the start pulse is measured (41) in the tag and a segment of the encrypted number is selected (42) in accordance with such width. A second tag pulse is generated at a time T after the start pulse arrives at the tag, the time T being dependent on the length of a variable time delay t.sub.v which is determined by the value of the bits in the selected segment of the encrypted number. At the reader, the total time from the beginning of the start pulse to the receipt of the second tag signal is measured (36, 37). The value of t.sub.v (21, 22, 23, 34) is known at the reader and the time T is subtracted (46) from the total time to find the actual propagation t.sub.p for signals to travel between the reader 11 and tag 12. The propagation time is then converted into distance (46).},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1992},
month = {1}
}

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