The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 16, 2002
Filed:
Dec. 23, 1997
Thomas Francis Johnston, London, GB;
ICO Services Ltd., London, GB;
Abstract
A satellite mobile telecommunications system includes mobile terminals which can communicate with one another using end-to end encryption and decryption techniques. When secure end-to-end communication is required, each terminal uses a common encryption code (RAND) to encode data and decode data transmitted between the terminals. The encryption code is transmitted in a secure manner from a remote database station ( ) to the terminals. Each terminal stores a terminal key (K , K ) on its SIM card and the keys are also held in the remote station ( ). Partial keys (K , K ) comprising the pseudo random number (RAND) and the keys K , K stored at the station ( ) are produced at the station ( ) by an exclusive OR process in order to mask the keys and the random number. The partial key K =K +(RAND) is sent to terminal At the terminal the partial key K is exclusive OR-ed with the locally stored terminal key K on the SIM card, so as to recover (RAND). The common code (RAND) is determined by the same process at terminal from K =K +(RAND) and the locally stored key K . The terminals then both run a GSM encryption algorithm (A5) to encrypt and decrypt transmitted data, on the basis of the common code (RAND).