Selective denial of encrypted high precision data by indirect ke

Details Selective denial of encrypted high precision data by indirect ke Selective denial of encrypted high precision data by indirect ke

1998-06-10

1999-11-09

Hayes, Gail O.

Cryptography

Particular algorithmic function encoding

Nbs/des algorithm

380 9, 342354, 342357, H04L 900, H04B 7185, G01S 502, H04K 102

Patent

active

059828978

ABSTRACT:
High precision transmitted navigational data as encrypted data transmitted by global positioning (GPS) satellites is made unavailable in regions designated as hostile and during desired intervals, while allowing the data to be available outside the hostile region. All satellites in the GPS constellation transmit the high precision navigational data in encrypted form. However, only the satellites that are not visible to the hostile region transmit the periodic key necessary to decrypt the data. The periodic key changes after a predetermined time interval. During a given time interval the same key value is used by all satellites for encryption of the high precision navigational data. A receiver can obtain the current periodic key from any visible satellite which is transmitting the periodic key. This key is then used to decrypt the high precision navigational data from that satellite and all other visible satellites. As a result, users in the hostile region are denied access to the high precision navigational data because they are unable to obtain the periodic key necessary to decrypt the data.

REFERENCES:
patent: 5444449 (1995-08-01), Poskett et al.
patent: 5640452 (1997-06-01), Murphy

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