Cryptography – Communication system using cryptography – Symmetric key cryptography
Reexamination Certificate
2007-04-17
2007-04-17
Song, Hosuk (Department: 2135)
Cryptography
Communication system using cryptography
Symmetric key cryptography
C380S044000, C380S046000
Reexamination Certificate
active
10640118
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.
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Kennedy Kevin
Olivier Steve
Pelkey Gary L.
Placek David M.
Donahue, III Dennis J. M.
Husch & Eppenberger LLC
Song Hosuk
Wegener Communications, Inc.
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