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Challenge-response badge

  • US 10,521,984 B1
  • Filed: 03/31/2015
  • Issued: 12/31/2019
  • Est. Priority Date: 03/31/2015
  • Status: Active Grant
First Claim
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1. An access-control system comprising:

  • a card reader configured to transmit a challenge message that includes a first sequence value;

    an access card configured to determine validity of the challenge message based at least in part on the first sequence value and a high-water-mark value stored on the access card, the high-water mark value based at least in part on a second sequence value associated with a previously-received valid challenge message, and in response to determining that the challenge message is valid, transmit a response message and update the high-water-mark value based at least in part on the first sequence value; and

    a security server configured to;

    determine that the response message is valid as a result of a timespan between a first recorded time when the challenge message is transmitted and a second recorded time when the response message is received does not exceed a threshold value; and

    as a result of determining that the response message is valid, cause an access control point device to grant access to an enclosed physical space.

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