Abstract: A portion of data is obfuscated by performing a bitwise XOR function between bits of the data portion and bits of a mask. The mask is generated based on the memory address of the data portion. A bitfield representing the memory address of the data portion is split into subset bitfields. Each subset then forms the input of a corresponding primary randomizing unit. Each primary randomizing unit is arranged to generate an output bitfield that appears to be randomly correlated with the input, but which may be determined from the input if certain secret information is known. The output of the primary randomizing units is input into a series of secondary randomizing units. Each secondary randomizing unit is arranged to input at least one bit of the output of every primary randomizing unit. The output of the secondary randomizing units are then combined by concatenation to form a data mask.

Abstract: A receiver for receiving a data stream comprises a filtering arrangement for filtering said received data stream and a processor. The filtering arrangement is arranged to load at least a part of said data stream, to filter at least part of said data stream and to read at least part of said data stream. The filtering arrangement has a first mode in which said steps are carried out and a second mode in which said processor is arranged to interrupt the steps carried out by said filtering arrangement.

Abstract: An embodiment comprises a semiconductor integrated circuit for restricting the rate at which data may be accessed from an external memory by a device coupled to the circuit. The rate of data access is restricted if the data access satisfies one or more conditions. For example, one of the conditions is that the device which is requesting the data is insecure. Another condition is that the requested data is privileged. A data access monitor is provided to monitor data accesses and to is arranged to generate an access signal to indicate whether the conditions are satisfied or not. A bandwidth comparator determines whether data access exceeds a threshold and, if so, the semiconductor integrated circuit is impaired to prevent further data access.

Abstract: A system including input circuitry for receiving from one of a plurality of sources at least one packet stream including a plurality of packets for providing audio, video, private data and/or associated information; at least one output for outputting at least one packet of the at least one packet stream to circuitry arranged to provide an output stream; wherein the system is arranged to provide a tag indicative of the source, the tag being associated with the at least one packet.

Abstract: A memory stores data in an encrypted form. A modifiable register stores a memory address, a0, defining a boundary separating the memory into two regions. The lower region stores data encrypted using a key B, and the upper region stores data encrypted using a different key A. Data stored on the boundary address is encrypted using key A. Accordingly, when data is read from a memory address a, key A is used to decrypt the data if a?a0, and key B is used if a<a0. However, when data is written to a memory address a, then key A is used to encrypt the data if a?a0+1, key B is used if a<a0+1. When data is written to the boundary address, a0, the position of the boundary is caused to increase by one unit.

Abstract: Circuitry for processing data includes a plurality of filters arranged in parallel. Input data is stored. The input data is applied to the plurality of filters to provide at least two parallel results. An operation is carried out with respect to the results.

Abstract: A semiconductor integrated circuit for the processing of conditional access television signals, the circuit including an input interface for receiving encrypted television signals and an output interface for output of decrypted television signals. Control signals broadcast with the television signals include control words and common keys. The common keys are received in encrypted form, encrypted according to a secret key unique to each semiconductor integrated circuit. The input interface is connected to a decryption circuit whereby the only manner of providing the common keys to the circuit are in encrypted form encrypted according to the secret key. Due to the monolithic nature of the circuit, no secrets are exposed and the system is secure.

Abstract: A memory stores data in an encrypted form. A modifiable register stores a memory address, a0, defining a boundary separating the memory into two regions. The lower region stores data encrypted using a key B, and the upper region stores data encrypted using a different key A. Data stored on the boundary address is encrypted using key A. Accordingly, when data is read from a memory address a, key A is used to decrypt the data if a?a0, and key B is used if a<a0. However, when data is written to a memory address a, then key A is used to encrypt the data if a?a0+1, key B is used if a<a0+1. When data is written to the boundary address, a0, the position of the boundary is caused to increase by one unit.

Abstract: A portion of data is obfuscated by performing a bitwise XOR function between bits of the data portion and bits of a mask. The mask is generated based on the memory address of the data portion. A bitfield representing the memory address of the data portion is split into subset bitfields. Each subset then forms the input of a corresponding primary randomizing unit. Each primary randomizing unit is arranged to generate an output bitfield that appears to be randomly correlated with the input, but which may be determined from the input if certain secret information is known. The output of the primary randomizing units is input into a series of secondary randomizing units. Each secondary randomizing unit is arranged to input at least one bit of the output of every primary randomizing unit. The output of the secondary randomizing units are then combined by concatenation to form a data mask.

Abstract: A system including input circuitry for receiving from one of a plurality of sources at least one packet stream including a plurality of packets for providing audio, video, private data and/or associated information; at least one output for outputting at least one packet of the at least one packet stream to circuitry arranged to provide an output stream; wherein the system is arranged to provide a tag indicative of the source, the tag being associated with the at least one packet.

Abstract: An embodiment comprises a semiconductor integrated circuit for restricting the rate at which data may be accessed from an external memory by a device coupled to the circuit. The rate of data access is restricted if the data access satisfies one or more conditions. For example, one of the conditions is that the device which is requesting the data is insecure. Another condition is that the requested data is privileged. A data access monitor is provided to monitor data accesses and to is arranged to generate an access signal to indicate whether the conditions are satisfied or not. A bandwidth comparator determines whether data access exceeds a threshold and, if so, the semiconductor integrated circuit is impaired to prevent further data access.

Abstract: A semiconductor integrated circuit for the processing of conditional access television signals, the circuit including an input interface for receiving encrypted television signals and an output interface for output of decrypted television signals. Control signals broadcast with the television signals include control words and common keys. The common keys are received in encrypted form, encrypted according to a secret key unique to each semiconductor integrated circuit. The input interface is connected to a decryption circuit whereby the only manner of providing the common keys to the circuit are in encrypted form encrypted according to the secret key. Due to the monolithic nature of the circuit, no secrets are exposed and the system is secure.

Abstract: A receiver for receiving a data stream comprises a filtering arrangement for filtering said received data stream and a processor. The filtering arrangement is arranged to load at least a part of said data stream, to filter at least part of said data stream and to read at least part of said data stream. The filtering arrangement has a first mode in which said steps are carried out and a second mode in which said processor is arranged to interrupt the steps carried out by said filtering arrangement.

Abstract: The invention relates to circuitry for processing data. The circuitry comprises a plurality of filters arranged in parallel and means for storing input data. The input data is applied to the plurality of filters to provide at least two parallel results and means for carrying out an operation with respect to the results.

Abstract: Error checking circuitry for performing error checks based on mathematical functions comprises a data input stage adapted to receive incoming data and at least one feedback signal, a register arranged to receive at a plurality of register input signals from the data input stage and to generate at least one signal to feedback to the data input stage, and multiplexing circuitry, wherein the multiplexing circuitry is provided in association with the register such that signal routes through the register are configurable to successively perform error checks based on different first and second mathematical functions.