Importance

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Abstract

A method and apparatus is disclosed for providing a secure wireless communication link between a mobile nomadic device and a base computing unit. A mobile sends a host certificate (Cert.sub.-- Mobile) to the base along with a randomly chosen challenge value (CH1) and a list of supported shared key algorithms ('SKCS'). The base determines if the Cert.sub.--Mobile is valid. If the Cert.sub.-- Mobile is not valid, then the base unit rejects the connection attempt. The base then sends a Cert.sub.--Base, random number (RN1) encrypted in mobile's public key and an identifier for the chosen SKCS to the mobile. The base saves the RN1 value and adds the CH1 value and the chosen SKCS to messages sent to the base. The mobile unit then validates the Cert.sub.-- Base, and if the certificate is valid, the mobile verifies under the public key of the base (Pub.sub.-- Base) the signature on the message. The signature is verified by taking the base message and appending it to CH1 and the list of shared key algorithms that the mobile provided in the first message. If the base signature is not valid, then the communication attempt is aborted. In the event that the base signature is valid, the mobile determines the value of RN1 by decrypting Pub.sub.-- Mobile, RN1 under the private key of the mobile. The mobile then generates RN2 and the session key, and encrypts RN2 under the Pub.sub.-- Base. The mobile sends the encrypted RN2 and E(Pub.sub.-- Mobile, RN1) to the base. The base then verifies the mobile signature using the Pub.sub.-- Mobile obtained from the Cert.sub.--Mobile. If the mobile signature is verified, the base decrypts E(Pub.sub.-- Base, RN2) using its private key. The base then determines the session key. The mobile and base may then enter a data transfer phase using encrypted data which is decrypted using the session key which is RN1 .sym.RN2.

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First Claim