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Authentication method and communication terminal and communication processing unit using the method

  • US 5,390,252 A
  • Filed: 12/22/1993
  • Issued: 02/14/1995
  • Est. Priority Date: 12/28/1992
  • Status: Expired due to Fees
First Claim
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1. In a communication system which includes a communication processing unit having a first authentication key Kb and performing communication processing, a communication terminal having a second authentication key Ka unique thereto and connected via a communication channel to said communication processing unit, and a storage storing said second authentication key Ka for authenticating said communication terminal and responsive to a request from said communication processing unit to provide thereto said second authentication key Ka, an authentication method whereby said communication processing unit verifies the validity of said communication terminal when receiving therefrom a communication request;

  • said authentication method including a step wherein said communication processing unit responds to a communication request signal from said communication terminal to determine if said communication request signal is a first one and if so, a first processing mode is executed and if not, a second processing mode is executed;

    A. said first processing mode comprising the steps;

    wherein said communication processing unit;

    (a) responds to said communication request from said communication terminal to acquire said second authentication key Ka of said communication terminal from said storage; and

    (b) generates authentication information Xbi enciphered by said first authentication key Kb and random information Yi and transmits an authentication request signal containing said pieces of information, to said communication terminal;

    wherein said communication terminal;

    (c) transmits information Ka[Yi] as an authentication response signal to said communication processing unit, said information Ka[Yi] being obtained by enciphering said random information Yi with said second authentication key Ka; and

    (d) stores said enciphered authentication information Xbi; and

    wherein said communication processing unit;

    (e) verifies said authentication response signal using said second authentication key Ka; and

    B. said second processing mode comprising the steps;

    wherein said communication terminal;

    (f) transmits to said communication processing unit a communication request signal containing said enciphered authentication information Xbi obtained by authentication processing executed in response to the previous communication request;

    wherein said communication processing unit;

    (g) deciphers said enciphered authentication information Xbi into a deciphered authentication key Kci;

    (h) generates new random information Yi; and

    (i) transmits an authentication request signal containing said random information Yi to said communication terminal;

    wherein said communication terminal;

    (j) enciphers said received random information Yi by said authentication key Kci and sends said enciphered random information as an authentication response signal to said communication processing unit; and

    wherein said communication processing unit;

    (k) verifies said received authentication response signal using said deciphered authentication key Kci.

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