Mr Ram

Topics: Power of two, Java, America's Next Top Model Pages: 2 (421 words) Published: June 19, 2013
Title:Descrambler Driver Modifications
Subtitle:BT Cardinal
Author:Jesus Matey
Date:February 21st, 2012
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1. Background Information
BT has noticed AV breakups every 10 seconds in all encrypted content. They occur exactly when new control words are set from CAK to the descrambler, via dscSetKeys(). These AV breakups are caused by 2 problems within the Broadcom CSD layer -Descrambler slot configuration occurs every time new control words (CW) are set, and not only when descrambling is started on a new channel -No check is performed at descrambler level to make sure that CW is not ret-set if it is the same as the previous one. Broadcom has confirmed that AV breakups can occur when modifying the CW currently being used by the descrambler 2. Scope of Modifications

AV Breakups Bug Fixing
Scope of changes is limited to csd.c, affecting:
-csdInitialize(), called during CAK initialization.
-csdTerminate(), called when closing a descrambler session (from dscClose()) -csdSetClearTextDescramblingKey(), called from dscSetKeys() Memory Leak Bug Fixing
A memory leak has been found and fixed, in csdSetClearTextDescramblingKey(). Delivery Format
We have taken this opportunity to modify the way we provide the Nagra CAS plugin server binary. Previously we have been providing a single binary, including the CSD library. We propose now to decouple the CSD library from other CAS plugin libraries. It is to be mentioned that we have only modified one makefile for this purpose. 3. Detailed Description of Modifications

CSD
We now keep a static table in RAM (16 entries), which uses pre-allocated memory to store current odd and even CW (up to 256 bytes per CW) for each active descrambler entry. -csdInitialize(): All table fields are set to default values when CAK is started -csdTerminate(): Table entry is freed when descrambler channel is closed -csdSetClearTextDescramblingKey():

oDescrambler slot configuration only occurs on the first...
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