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Claims  |
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We claim:
1. A subscriber unit in a hacking prevention system for use with a network
including a transmitter which transmits information to a multiplicity of
subscriber units, wherein each of the multiplicity of subscriber units is
independently enabled by a descrambling secret number, and when enabled is
responsive to data received from the transmitter for descrambling
scrambled information, the subscriber unit comprising:
a packet receiver unit for receiving a data stream including a series of
authorization packets, and a series of offset values, wherein each offset
value in said series of offset values is paired with a corresponding
authorization packet in said series of authorization packets;
a random number generator for providing a random number integer in the
range between one and the total number of packets in said series of
authorization packets;
a packet provider for providing to a removable smart card a selected
packet, wherein said selected packet is a packet having a serial number in
the series of authorization packets which is equal to said random number
integer; and
a descrambler including:
a key receiver for receiving from said removable smart card a key which
uniquely corresponds to said selected packet, and for receiving from said
packet provider an offset value which is paired with said selected packet;
and
a secret number generator utilizing the key with the offset value which is
paired with said selected packet to produce said descrambling secret
number,
whereby said key and said selected packet intercepted at a first subscriber
unit cannot be effective to enable a second subscriber unit.
2. A subscriber unit according to claim 1 and wherein the packet receiver
unit, the random number generator, the packet provider, and the
descrambler are embodied in a single VLSI chip.
3. A system according to claim 2 wherein each of said multiplicity of
subscriber units comprises said single VLSI chip.
4. A subscriber unit according to claim 1 and wherein said network is a
CATV network and said subscriber units are CATV receivers and decoders.
5. A hacking prevention method for use with a network including a
transmitter which transmits information to a multiplicity of subscriber
units, wherein each of the multiplicity of subscriber units is
independently enabled by a descrambling secret number, and when enabled is
responsive to data received from the transmitter for descrambling
scrambled information, the method comprising the steps of:
receiving a data stream including a series of authorization packets, and a
series of offset values, wherein each offset value in said series of
offset values is paired with a corresponding authorization packet in said
series of authorization packets;
generating a random number integer in the range between one and the total
number of packets in said series of authorization packets;
providing a selected packet, wherein said selected packet is a packet
having a serial number in the series of authorization packets which is
equal to said random number integer;
producing a key which uniquely corresponds to said selected packet; and
generating a descrambling secret number which is the same for all of said
multiplicity of subscriber units by utilizing the key with the offset
value which is paired with said selected packet,
whereby said key and said selected packet intercepted at a first subscriber
unit cannot be effective to enable a second subscriber unit.
6. A hacking prevention method according to claim 5 and wherein the step of
generating a random number integer and the step of generating a
descrambling secret number are executed in a single VLSI chip.
7. A hacking prevention method according to claim 5 and wherein the step of
producing a key, the step of generating a random number integer and the
step of generating a descrambling secret number are all executed in each
one of said multiplicity of subscriber units.
8. A hacking prevention method according to claim 5 and wherein said method
is employed in a CATV network and wherein said step of generating a random
number integer and said step of generating a descrambling secret number
are executed in CATV receivers and decoders.
9. A hacking prevention method according to claim 5 and wherein said step
of generating a random number integer, said step of generating a
descrambling secret number, and said step of producing a key are executed
in a single VLSI chip.
10. A hacking prevention method according to claim 5 and wherein said step
of generating a random number integer and said step of generating a
descrambling secret number are executed in a first VLSI chip, and said
step of producing the key is generated in a second VLSI chip.
11. A hacking prevention method according to claim 5 and wherein said step
of generating a random number integer and said step of generating a
descrambling secret number are executed in each one of said multiplicity
of subscriber units, and said step of producing a key is executed in each
one of a multiplicity of smart cards, each associated with one of said
multiplicity of subscriber units.
12. A subscriber unit in a system for selective transmission of information
to a multiplicity of subscribers which subscribers may be individually
characterized by at least one of the following parameters: information
suppliers, geographic locations, and demographics, wherein information is
transmitted from an information source to a multiplicity of subscribers
which fall into different groups according to at least one of said
parameters, each group being entitled to receive at least a portion of the
information, the system being employed in a network including a
transmitter and a multiplicity of subscriber units, wherein each of the
multiplicity of subscriber units is associated with a subscriber and is
independently enabled by a descrambling secret number and when enabled
being responsive to data received from the transmitter for descrambling
scrambled information, the subscriber unit comprising:
a packet receiver unit for receiving a data stream including a series of
authorization packets, a first series of offset values, and a second
series of offset values, wherein each offset value in said first series of
offset values is paired with a corresponding authorization packet in said
series of authorization packets, and each offset value in said second
series of offset values identifies a group of subscribers characterized by
at least one of said parameters;
a random number generator for providing a random number integer in the
range between one and the total number of packets in said series of
authorization packets;
a packet provider for providing to a removable smart card a selected
packet, wherein said selected packet is a packet having a serial number in
the series of authorization packets which is equal to said random number
integer; and
a descrambler including:
a key receiver for receiving from said removable smart card a key which
uniquely corresponds to said, selected packet, and for receiving from said
packet provider a first offset value which is paired with said selected
packet, and a second offset value which identifies said subscriber unit as
belonging to a group of subscribers characterized by at least one of said
parameters; and
a secret number generator utilizing the key, the first offset value which
is paired with said selected packet, and the second offset value to
produce said descrambling secret number,
whereby said key and said selected packet intercepted at a first subscriber
unit cannot be effective to enable a second subscriber unit, and
whereby said second offset value intercepted at a subscriber unit which
forms part of a first group of subscriber units cannot be effective to
enable a subscriber unit which forms part of a second group of subscriber
units.
13. A subscriber unit according to claim 12 and wherein the packet receiver
unit, the random number generator, the packet provider and the descrambler
are embodied in a single VLSI chip.
14. A system according to claim 13 wherein each of said multiplicity of
subscriber units comprises said single VLSI chip.
15. A subscriber unit according to claim 12 and wherein said network is a
CATV network and said subscriber units are CATV receivers and decoders.
16. A method for selective transmission of information to a multiplicity of
subscribers which subscribers may be individually characterized by at
least one of the following parameters: information suppliers, geographic
locations, and demographics, wherein information is transmitted from an
information source to a multiplicity of subscribers which fall into
different groups according to at least one of said parameters, each group
being entitled to receive at least a portion of the information, the
method being employed in a network including a transmitter and a
multiplicity of subscriber units, wherein each subscriber unit is
associated with a subscriber and is independently enabled by a
descrambling secret number and when enabled is responsive to data received
from the transmitter for descrambling scrambled information, the method
comprising the steps of:
receiving a data stream including a series of authorization packets, a
first series of offset values, and a second series of offset values,
wherein each offset value in said first series of offset values is paired
with a corresponding authorization packet in said series of authorization
packets, and each offset value in said second series of offset values
identifies a group of subscribers characterized by at least one of said
parameters;
generating a random number integer in the range between one and the total
number of packets in said series of authorization packets;
providing a selected packet, wherein said selected packet is a packet
having a serial number in the series of authorization packets which is
equal to said random number integer;
producing a key which uniquely corresponds to said selected packet; and
generating, at a subscriber unit, a descrambling secret number which is the
same for all of said multiplicity of subscriber units by utilizing the
key, a first offset value which is paired with said selected packet, and a
second offset value which identifies said subscriber unit as belonging to
a group of subscribers characterized by at least one of said parameters,
whereby said key and said selected packet intercepted at a first subscriber
unit cannot be effective to enable a second subscriber unit, and
whereby said second offset value intercepted at a subscriber unit which
forms part of a first group of subscriber units cannot be effective to
enable a subscriber unit which forms part of a second group of subscriber
units.
17. A method according to claim 16 and wherein the step of generating a
random number integer and the step of generating a descrambling secret
number are executed in a single VLSI chip.
18. A method according to claim 16 and wherein the step of producing a key,
the step of generating a random number integer, and the step of generating
a descrambling secret number are all executed in each one of said
multiplicity of subscriber units.
19. A method according to claim 16 and wherein said method is employed in a
CATV network and wherein said step generating a random number integer and
said step of generating a descrambling secret number are executed in CATV
receivers and decoders.
20. A method according to claim 16 and wherein said step of generating a
random number integer, said step of generating a descrambling secret
number, and said step of producing a key are executed in a single VLSI
chip.
21. A method according to claim 16 and wherein said step of generating a
random number integer and said step of generating a descrambling secret
number are executed in a first VLSI chip, and said step of producing a key
is generated in a second VLSI chip.
22. A method according to claim 16 and wherein said step of generating a
random number integer and said step of generating a descrambling secret
number are executed in each one of said multiplicity of subscriber units,
and said step of producing a key is executed in each one of a multiplicity
of smart cards, each associated with one of said multiplicity of
subscriber units.
23. A hacking prevention system comprising:
a communication network;
a transmitter for transmitting, via said communication network, scrambled
information associated with a series of authorization packets which are
employed to authorize subscribers to access the information in clear form,
and with a series of offset values, wherein each offset value in said
series of offset values is paired with a corresponding authorization
packet in said series of authorization packets; and
a multiplicity of subscriber units, each including:
a communication receiver and decoder which is operative to receive said
scrambled information, said series of authorization packets and said
series of offset values, and to provide an output including a selected one
of said authorization packets, selected in accordance with a random number
algorithm; and
a smart card, coupled to said communication receiver and decoder, and
operative to receive said output including a selected one of said
authorization packets and to provide to said communication receiver and
decoder a key which uniquely corresponds to said selected one of said
authorization packets, wherein
said communication receiver and decoder employs said key and an offset
value which is paired with said selected one of said authorization packets
to generate a secret number which is used by said communication receiver
and decoder to descramble said scrambled information, said secret number
being the same for all of said multiplicity of subscriber units.
24. A hacking prevention system comprising:
a communication network;
a transmitter for transmitting, via said communication network, scrambled
information associated with a series of authorization packets which are
employed to authorize subscribers to access the information in clear form,
with a first series of offset values, and with a second series of offset
values, wherein each offset value in said first series of offset values is
paired with a corresponding authorization packet in said series of
authorization packets, and each offset value in said second series of
offset values identifies a group of subscribers characterized by at least
one of the following parameters: information suppliers, geographic
locations, and demographics; and
a multiplicity of subscriber units, each including:
a communication receiver and decoder which is operative to receive said
scrambled information, said series of authorization packets, said series
of first offset values, and said series of second offset values, and to
provide an output including a selected one of said authorization packets,
selected in accordance with a random number algorithm; and
a smart card, coupled to said communication receiver and decoder, and
operative to receive said output including a selected one of said
authorization packets and to provide to said communication receiver and
decoder a key which uniquely corresponds to said selected one of said
authorization packets, wherein
said communication receiver and decoder employs said key, a first offset
value which is paired with said selected one of said authorization
packets, and a second offset value which identifies said communication
receiver and decoder as being part of a subscriber unit which belongs to a
group of subscribers characterized by at least one of said parameters to
generate a secret number which is used by said communication receiver and
decoder to descramble said scrambled information, said secret number being
the same for all of said multiplicity of subscriber units.
25. A subscriber unit for use with a network including a transmitter which
transmits information to a multiplicity of subscriber units, wherein each
of the multiplicity of subscriber units is independently enabled by a
decrypting secret number, and when enabled being responsive to data
received from the transmitter for decrypting encrypted information, the
subscriber unit comprising:
a packet receiver unit for receiving, via said network, a data stream
including a series of authorization packets, and a series of offset
values, wherein each offset value in said series of offset values is
paired with a corresponding authorization packet in said series of
authorization packets;
a random number generator for providing a random number integer in the
range between one and the total number of packets in said series of
authorization packets;
a packet provider for providing to a removable smart card a selected
packet, wherein said selected packet is a packet having a serial number in
the series of authorization packets which is equal to said random number
integer; and
a decrypter including:
a key receiver for receiving from said removable smart card a key which
uniquely corresponds to said selected packet, and for receiving from said
packet provider an offset value which is paired with said selected packet;
and
a secret number generator utilizing the key with the offset value which is
paired with said selected packet to produce said decrypting secret number,
whereby said key and said selected packet intercepted at a first subscriber
unit cannot be effective to enable a second subscriber unit.
26. A subscriber unit for use with a network including a transmitter which
transmits information to a multiplicity of subscriber units, wherein each
of the multiplicity of subscriber units is independently enabled by a
descrambling secret number, and when enabled being responsive to data
received from the transmitter for descrambling scrambled information, the
subscriber unit comprising:
a packet receiver unit for receiving, via said network, a data stream
including a series of authorization packets, and a series of offset
values, wherein each offset value in said series of offset values is
paired with a corresponding authorization packet in said series of
authorization packets;
a random number generator for providing a random number integer in the
range between one and the total number of packets in said series of
authorization packets;
a packet provider for providing a selected packet, wherein said selected
packet is a packet having a serial number in the series of authorization
packets which is equal to said random number integer; and
a descrambler including:
a key receiver for receiving from said packet provider said selected packet
and an offset value which is paired with said selected packet;
a key producer for producing a key which uniquely corresponds to said
selected packet; and
a secret number generator utilizing the key with the offset value which is
paired with said selected packet to produce said descrambling secret
number,
whereby said selected packet and said offset value which is paired with
said selected packet intercepted at a first subscriber unit cannot be
effective to enable a second subscriber unit.
27. A subscriber unit in a system for selective transmission of information
to a multiplicity of subscribers which subscribers may be individually
characterized by at least one of the following parameters: information
suppliers, geographic locations, and demographics, wherein information is
transmitted from an information source to a multiplicity of subscribers
which fall into different groups according to at least one of said
parameters, each group being entitled to receive at least a portion of the
information, the system being employed in a network including a
transmitter and a multiplicity of subscriber units, wherein each of the
multiplicity of subscriber units is associated with a subscriber and is
independently enabled by a descrambling secret number and when enabled
being responsive to data received from the transmitter for descrambling
scrambled information, the subscriber unit comprising:
a packet receiver unit for receiving, via said network, a data stream
including a series of authorization packets, a first series of offset
values, and a second series of offset values, wherein each offset value in
said first series of offset values is paired with a corresponding
authorization packet in said series of authorization packets, and each
offset value in said second series of offset values identifies a group of
subscribers characterized by at least one of said parameters;
a random number generator for providing a random number integer in the
range between one and the total number of packets in said series of
authorization packets;
a packet provider for providing a selected packet, wherein said selected
packet is a packet having a serial number in the series of authorization
packets which is equal to said random number integer; and
a descrambler including:
a key receiver for receiving from said packet provider said selected
packet, a first offset value which is paired with said selected packet,
and a second offset value which identifies said subscriber unit as
belonging to a group of subscribers characterized by at least one of said
parameters;
a key producer for producing a key which uniquely corresponds to said
selected packet; and
a secret number generator utilizing the key, the first offset value which
is paired with said selected packet, and the second offset value to
produce said descrambling secret number,
whereby said selected packet, said first offset value and said second
offset value intercepted at a subscriber unit which forms part of a first
group of subscriber units cannot be effective to enable a subscriber unit
which forms part of a second group of subscriber units.
28. A hacking prevention method comprising:
providing a communication network including a transmitter and a
multiplicity of subscriber units;
transmitting, via said communication network, scrambled information
associated with a series of authorization packets which are employed to
authorize subscribers to access the information in clear form, and with a
series of offset values, wherein each offset value in said series of
offset values is paired with a corresponding authorization packet in said
series of authorization packets;
receiving, at a subscriber unit, said scrambled information, said series of
authorization packets and said series of offset values;
coupling a removable smart card to said subscriber unit;
outputting, to said smart card, a selected one of said authorization
packets, selected in accordance with a random number algorithm;
employing, at said smart card, the selected one of said authorization
packets received thereat to produce a key which uniquely corresponds to
said selected one of said authorization packets;
transmitting said key to the subscriber unit; and
generating, at said subscriber unit, a secret number by employing said key
and an offset value which is paired with said selected one of said
authorization packets, wherein said secret number is used by said
subscriber unit to descramble said scrambled information.
29. A hacking prevention method comprising:
providing a communication network including a transmitter and a
multiplicity of subscriber units;
transmitting, via said communication network, scrambled information
associated with a series of authorization packets which are employed to
authorize subscribers to access the information in clear form, with a
first series of offset values, and with a second series of offset values,
wherein each offset value in said first series of offset values is paired
with a corresponding authorization packet in said series of authorization
packets, and each offset value in said second series of offset values
identifies a group of subscribers characterized by at least one of the
following parameters: information suppliers, geographic locations, and
demographics;
receiving, at a subscriber unit, said scrambled information, said series of
authorization packets, said series of first offset values, and said series
of second offset values;
coupling a removable smart card to said subscriber unit;
outputting, to said smart card, a selected one of said authorization
packets, selected in accordance with a random number algorithm;
employing, at said smart card, the selected one of said authorization
packets received thereat to produce a key which uniquely corresponds to
said selected one of said authorization packets;
transmitting said key to the subscriber unit; and
generating, at said subscriber unit, a secret number by employing said key,
a first offset value which is paired with said selected one of said
authorization packets, and a second offset value which identifies the
subscriber unit as belonging to a group of subscribers characterized by at
least one of said parameters, wherein said secret number is used by said
subscriber unit to descramble said scrambled information. |
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Claims |
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Description |
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FIELD OF THE INVENTION
The present invention relates generally to secure communication systems and
more particularly to systems wherein encrypted information is transmitted
from a single location to multiple terminals located at non-secure
locations.
BACKGROUND OF THE INVENTION
A major problem in secure communication systems is the possibility of
unauthorized penetration. Unauthorized penetration of this kind is
referred to as hacking.
Several methods have been employed to overcome the problem of hacking.
Encryption of transmitted data and authentication of communicators are
some of the methods employed to make hacking more difficult.
One hacking method which is considered difficult to overcome is called "The
McCormac Hack". This method, which is believed to be theoretically
applicable to CATV systems, is described in the book "World Satellite TV
and Scrambling Methods", 2nd Edition, Baylin Publications 1991, pp.
243-244 by Frank Baylin, Richard Maddox and John McCormac and in
"Satellite Watch News", August 1991. According to this method, a data
stream from a legitimately authorized decoder, is extracted in real time
and transmitted over the air using a small radio-frequency (RF)
transmitter. The data stream is then used to activate a number of pirate
decoders.
SUMMARY OF THE INVENTION
The present invention seeks to provide methods and systems which
substantially prevent the possibility of extracting a data stream from a
legitimately authorized terminal and transmitting the data stream to a
plurality of pirate terminals.
For the purposes of the present invention, the term "terminals" in all of
its forms is used in a broader than usual sense to cover all types of
computer terminals, CATV decoders, remote computers and remote
computerized stations.
For the purposes of the present invention, the terms "seed" and "key" in
all of their forms are alternately used in a broader than usual sense to
cover all types of numbers or other symbols, either secret or non-secret,
which are used at least as part of encryption/decryption keys to
encrypt/decrypt (or scramble/descramble) data. The term "secret number"
will be further used, for the purpose of the present invention, to denote
the secret key which is used for encryption/decryption (or
scrambling/descrambling) of data.
There is thus provided in accordance with a preferred embodiment of the
present invention a hacking prevention system for use with a system
including a transmitter and a multiplicity of receivers, each receiver
being independently enabled by a secret number and when enabled being
responsive to data received from the transmitter for decrypting encrypted
information, each of the multiplicity of receivers having associated
therewith:
a first key generator, employing at least part of the data and a function
which differs for at least a plurality of ones of said multiplicity of
receivers, for generating a first key which is different for each receiver
having a different function;
a second key generator employing at least part of the data and said
function to produce a second key; and
a secret number generator utilizing the first key with the second key to
produce said secret number which is the same for all of said multiplicity
of receivers,
whereby first and second keys intercepted at a first receiver cannot be
effective to enable a second receiver having a different function.
Additionally in accordance with a preferred embodiment of the present
invention there is provided a hacking prevention method for use with a
network including a transmitter and a multiplicity of receivers, each
receiver being independently enabled by a secret number and when enabled
being responsive to data received from the transmitter for decrypting
encrypted information, the method comprising the steps of:
generating a first key, by employing at least part of the data and a
function which differs for at least a plurality of ones of the
multiplicity of receivers, the first key being different for each receiver
having a different function;
generating a second key by employing at least part of the data and the
function; and
generating a secret number by utilizing the first key with the second key
to produce the secret number which is the same for all of the multiplicity
of receivers,
whereby first and second keys intercepted at a first receiver cannot be
effective to enable a second receiver having a different function.
Additionally in accordance with a preferred embodiment of the present
invention there is provided a system for selective transmission of
information to a multiplicity of subscribers which subscribers may be
individually characterized by at least one of the following parameters:
information suppliers, geographic locations, and demographics, wherein
information is transmitted from an information source to a multiplicity of
subscribers which fall into different groups according to at least one of
the parameters, each group being entitled to receive at least a portion of
the information, the system being employed in a network including a
transmitter and a multiplicity of receivers, each receiver associated with
a subscriber and being independently enabled by a secret number and when
enabled being responsive to data received from the transmitter for
decrypting encrypted information, each of the multiplicity of receivers
comprising:
a first key generator, employing at least part of the data and a function
which differs for at least a plurality of ones of the multiplicity of
receivers, for generating a first key which is different for each receiver
having a different function;
a second key generator employing at least part of the data and the function
to produce a second key;
a third key generator employing at least part of the data to provide a key
which is characterized by at least one of the parameters; and
a secret number generator utilizing the first key, the second key and the
third key to produce the secret number which is the same for all of the
multiplicity of receivers,
whereby first and second keys intercepted at a first receiver cannot be
effective to enable a second receiver having a different function, and
whereby a third key intercepted at a receiver which forms part of a first
group of receivers cannot be effective to enable a receiver which forms
part of a second of the group of receivers.
Further in accordance with a preferred embodiment of the present invention
there is provided a method for selective transmission of information to a
multiplicity of subscribers which subscribers may be individually
characterized by at least one of the following parameters: information
suppliers, geographic locations, and demographics, wherein information is
transmitted from an information source to a multiplicity of subscribers
which fall into different groups according to at least one of the
parameters, each group being entitled to receive at least a portion of the
information, the method being employed in a network including a
transmitter and a multiplicity of receivers, each receiver associated with
a subscriber and being independently enabled by a secret number and when
enabled being responsive to data received from the transmitter for
decrypting encrypted information, the method comprising the steps of:
generating a first key by employing at least part of the data and a
function which differs for at least a plurality of ones of the
multiplicity of receivers, for generating a first key which is different
for each receiver having a different function;
generating a second key by employing at least part of the data and the
function to produce a second key;
generating a third key by employing at least part of the data to provide a
key which is characterized by at least one of the parameters; and
generating a secret number utilizing the first key, the second key and the
third key to produce the secret number which is the same for all of the
multiplicity of receivers,
whereby first and second keys intercepted at a first receiver cannot be
effective to enable a second receiver having a different function, and
whereby a third key intercepted at a receiver which forms part of a first
group of receivers cannot be effective to enable a receiver which forms
part of a second of the group of receivers.
In accordance with a preferred embodiment of the present invention, the
function which differs for at least a plurality of ones of said
multiplicity of receivers, is a random generator.
Preferably, the second key generator is embodied in a single VLSI chip.
In accordance with a preferred embodiment of the present invention, the
VLSI chip is mounted on a smart card.
Preferably, the first key generator, the function and the secret number
generator are embodied in a single VLSI chip.
In accordance with a preferred embodiment of the present invention, the
first key generator, the function, the secret number generator and the
second key generator are embodied in a single VLSI chip.
Preferably, each of said multiplicity of receivers comprises at least one
of said VLSI chips.
In accordance with a preferred embodiment of the invention, the network is
a CATV network and said multiplicity of receivers are CATV receivers and
decoders.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood and appreciated more fully from
the following detailed description, taken in conjunction with the drawings
in which:
FIG. 1 is a generalized block diagram illustration of a theoretical hacking
system based on the prior art "McCormac Hack" method;
FIG. 2 is a generalized block diagram illustration of part of a subscriber
unit constructed and operative in accordance with a preferred embodiment
of the present invention;
FIG. 3 is a flowchart description of the functionality of the apparatus of
FIG. 2;
FIG. 4 is a flowchart description of the functionality of the apparatus of
FIG. 2 in accordance with an alternative embodiment of the invention which
does not employ conditional access cards;
FIG. 5 is a generalized block diagram illustration of part of a subscriber
unit in accordance with a preferred embodiment of the invention in which
receivers characterized by different parameters are enabled with the same
secret number; and
FIG. 6 is a flowchart description of the functionality of the apparatus of
FIG. 5.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Reference is now made to FIG. 1, which is a generalized block diagram
illustration of a theoretical hacking system constructed and operative in
accordance with the prior art "McCormac Hack" method.
An authorized decoder 10, which is normally operated by a valid smart card
12, is coupled instead to a McCormac's Hack Interface (MHI) unit 14 via a
standard smart card communication link 15. Smart card 12 is also coupled
to the MHI unit 14 via a standard smart card communication link 16.
MHI unit 14 "sniffs" the communication data passed between the smart card
12 and the authorized decoder 10 and provides it to a small radio
transmitter 18. Radio transmitter 18 transmits the data via a
radio-frequency (RF) link 19 to a radio receiver 20 which is coupled to a
virtual smart card unit 22. Virtual smart card unit 22 is coupled to an
unauthorized decoder 24 via a standard smart card communication link 25.
In this way the unauthorized decoder 24 is operated by the same data
stream that operates the authorized decoder 10.
In an alternative embodiment, MHI unit 14 "sniffs" the data which is
communicated between units inside the authorized decoder 10. In this
embodiment, MHI unit 14 is linked, via communication link 27, to a
communication BUS 26 extending between a micro-processor 28 and a
descrambling device 29. Communication BUS 26 carries the "seed" value
which is the secret number required for descrambling. In this way the seed
value may be extracted and transmitted to the unauthorized decoder for
descrambling of the data.
Reference is now made to FIG. 2, which is a generalized block diagram
illustration of part of a subscriber unit constructed and operative in
accordance with a preferred embodiment of the present invention.
In accordance with a preferred embodiment of the present invention, a data
stream including a series of authorization packets PKT1, . . . ,PKTn is
transmitted from an information source via a satellite link, to a packet
receiver and descrambler unit 30 which forms part of a subscriber's CATV
receiver and decoder (not shown). A series of offset values DELTA1, . . .
,DELTAn is also transmitted via the satellite link and received by the
packet receiver and descrambler unit 30. Preferably, each packet is paired
with an offset value.
In the packet receiver and descrambler unit 30 a Packet Receiver Unit (PRU)
32 receives the series of packets and the offset values. A random number
generator 34 provides a number in the range 1, . . . ,n to PRU 32 by
employing a random number algorithm. According to the selected number, for
example 3, the corresponding packet, i.e. PKT3, is transmitted to a smart
card 36 and a corresponding offset value, i.e. DELTA3, which serves as an
internal key, is transmitted to a descrambler unit 38.
Smart card 36 employs an algorithm which produces an appropriate seed for
each packet. When smart card 36 receives PKT3 it produces a corresponding
key, here termed SEED3, and provides it to the descrambler unit 38.
It is to be appreciated that PRU 32, random number generator 34 and the
descrambler unit 38 are all embodied in a secure chip such as a VLSI chip.
Thus, the communication of the random number and the offset value cannot
be altered or "sniffed".
In the descrambler unit 38 the keys DELTA3 and SEED3 received from PRU 32
and smart card 36 respectively are employed by a function f such that:
(1) f=f(seed value, offset value), and
(2) SEED0=f(SEEDi,DELTAi) for any i=1, . . . ,n,
where SEED0 is the secret number required for descrambling of the data and
"i" is any integer value in the series 1, . . . ,n. If the value i=3 is
selected then:
(3) SEED0=f(SEED3,DELTA3).
In accordance with a preferred embodiment of the present invention, the
descrambler 38 functions as a secret number generator in generating the
SEED0 value and also functions as a key receiver, which receives an
internal key and a key from the smart card. The SEED0 value is employed by
the descrambler 38 for descrambling of the data. Inasmuch as the
descrambler 38 is in a VLSI format it is considered difficult, if not
practically impossible, to tap the SEED0 value.
It is to be appreciated that the hacking prevention system of FIG. 2 may be
also operable with systems which do not employ smart cards. In that case
the seed values corresponding to the packets PKT1, . . . ,PKTn may be
calculated and produced in any suitable part of the packet receiver and
descrambler 30, such as, for example, any one of PRU 32, random number
generator 34 and descrambler 38, by employing an algorithm which is
similar to the one employed in the smart card. Upon receipt of the
selected random number from random number generator 34, the corresponding
calculat | | |
