Selective denial of encrypted high precision data by indirect keying
US5982897A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 10, 1998 |
| Grant date | Nov 9, 1999 |
| Priority date | — |
| Expiry date | Jun 10, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B7/18593
- WIPO fieldMeasurement
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.