US 5,237,610 A · Independent external security module for a digitally upgradeable television signal decoder

Abstract

A decoder for descrambling encoded satellite transmissions comprises an internal security module and a resplaceable security module. The program signal is scrambled with a key and then the key itself is twice-encrypted and multiplexed with the scrambled program signal. The key is first encrypted with a first secret serial number (SSN.sub.1) which is assigned to a given replaceable security module. The key is then encrypted with a second secret serial number (SSN.sub.2) which is assigned to a given decoder. The decoder performs a first key decryption using the second secret serial number (SSN.sub.2) stored within the decoder. The partially decrypted key is then further decrypted by the replaceable security module using the first secret serial number (SSN.sub.1) stored within the replaceable security module. The decoder then descrambles the program using the twice-decrypted key. The replaceable security module can be replaced, allowing the security system to be upgraded or changed following a system breach. Either security module may become the active security module to finally decrypt the seed, selectable by a signal transmitted from the encoder. Also disclosed is a method for transmitting the encrypted keys and secret serial numbers to a plurality of broadcasters who may in turn multiplex this signal with their own program signals so that any given channel received by a subscriber contains the key and secret serial numbers. Additionally, the decoder may be upgradeable to accept both analog and digital video signals without significant redundant circuitry.

Claims28

Dependent claims

A security system for transmission of a signal comprising:

encoder means for encoding said signal, said encoder means comprising:
signal scrambling means for scrambling said signal and outputting a scrambled signal and key for descrambling said scrambled signal,
first key encryptor means coupled to said signal scrambling means, for selectively performing a first encryption on said key using a first confidential serial number and outputting an encrypted key,
second key encryptor means coupled to said scrambling means for selectively performing a second encryption on said key using a second confidential serial number and outputting an encrypted key, and
decoder means coupled to said transmission means for receiving and descrambling said scrambled signal, said decoder means comprising:
first key decryptor means coupled to said transmission means, for performing a first key decryption on said encrypted key using said first confidential serial number if said key was encrypted with said first confidential serial number,
a replaceable security module, removably attached to said decoder means and containing a second key decryptor means coupled to said transmission means, for performing a second key decryption on said encrypted key using a second confidential serial number if said encrypted key was encrypted with said second confidential serial number, and
signal descrambling means coupled to said first and second key decryptor means, and said transmission means for descrambling said scrambled signal using said decrypted key.

5 more elements

Dependencies are inferred from the claim text.

Independent external security module for a digitally upgradeable television signal decoder

Life of this patent

Independent external security module for a digitally upgradeable television signal decoder

Life of this patent

Abstract

Claims28