Rapid decryption of data by key synchronization and indexing
US7206411B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 13, 2003 |
| Grant date | Apr 17, 2007 |
| Priority date | — |
| Expiry date | Aug 31, 2025 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2209/601
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A satellite broadcast conditional access system with key synchronization uses indexing of an authorization stream to quickly restart the decrypting process after short carrier fades and after carrier switches. The authorization stream includes cyphered seeds and index numbers which are sequentially sent to a group of receivers. The same authorization stream can also be broadcast multiple times to the group of receivers. A conditional access server selects a starting index number and increments the index number by a predefined value. The receivers have a memory to save the current index number for the authorization stream. Any receiver that loses its connection to the broadcast and thereafter reestablishes its connection can retrieve the latest index number being issued in the authorization stream and compare it with the stored index number. When the index numbers match or are within a defined threshold, the receiver will continue to decypher the seeds and decrypt the transport stream.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.