Abstract: A heterogeneous array includes clusters of processing elements. The clusters include a combination of ALUs and multiplexers linked by direct connections and various general-purpose routing networks. The multiplexers are controlled by the ALUs in the same cluster, or alternatively by ALUs in other clusters, via a special purpose routing network. Components of applications configured onto the array are selectively implemented in either multiplexers or ALUs, as determined by the relative efficiency of implementing the component in one or the other type of processing element, and by the relative availability of the processing element types. Multiplexer control signals are generated from combinations of ALU status signals, and optionally routed to control multiplexers in different clusters.

Abstract: A method of and an apparatus for implementing real-time transaction specific watermarking to generate a transaction specific digitally watermarked data file is described. The method comprises two stages. Prior to receiving (52; 102) a transaction request for the data file: the data file is divided (34; 84) into a plurality of sections; and a set of pre-calculated elementary watermarks is created (86). On receiving (52; 102) a transaction request for the supply of the data file: the method comprises calculating (56; 106) a transaction specific watermark; selecting (64; 114) pre-calculated elementary watermarks equivalent to constituent portions of the transaction specific watermark by comparing the constituent portions of the transaction specific watermark with the pre-calculated units of data; and constructing (66; 116, 118) a transaction specific watermarked data file by assembling the selected pre-calculated elementary watermarks together with corresponding ones of the plurality of sections.

Abstract: Power supply voltages are selectively modulated to correspond with degraded input voltages to a logic device. Modulated power supply voltages are provided to transistors within the logic device, so that the degraded input voltages supplied to the transistors are sufficient to turn the transistors substantially on or off. Leakage currents are prevented thereby from flowing across the transistors.

Abstract: Power supply voltages are selectively modulated to correspond with degraded input voltages to a logic device. Modulated power supply voltages are provided to transistors within the logic device, so that the degraded input voltages supplied to the transistors are sufficient to turn the transistors substantially on or off. Leakage currents are prevented thereby from flowing across the transistors.

Abstract: A method of and an apparatus for implementing real-time transaction specific watermarking to generate a transaction specific digitally watermarked data file is described. The method comprises two stages. Prior to receiving (52; 102) a transaction request for the data file: the data file is divided (34; 84) into a plurality of sections; and a set of pre-calculated elementary watermarks is created (86). On receiving (52; 102) a transaction request for the supply of the data file: the method comprises calculating (56; 106) a transaction specific watermark; selecting (64; 114) pre-calculated elementary watermarks equivalent to constituent portions of the transaction specific watermark by comparing the constituent portions of the transaction specific watermark with the pre-calculated units of data; and constructing (66; 116, 118) a transaction specific watermarked data file by assembling the selected pre-calculated elementary watermarks together with corresponding ones of the plurality of sections.

Abstract: A communication bridge interconnecting two or more local area networks. Input buffers forward packet headers of received data packets through to a routing engine. The routing engine contains one or more routing tables each having a plurality of table locations containing table data in the form of station addresses and routing data. The table is accessed by applying a hashing algorithm to a received destination address contained in the data packet to determine the table location and then checking that the station address retrieved from the table location corresponds with the destination address in the received data packet.

Abstract: A secure information storage system in which a directory stores identifying titles and pointers to areas of a memory storing respective messages. To protect the messages against unauthorized changes, a MAC (message authentication code) is calculated for them in known manner and stored in a register in a secure unit. This involves processing the whole of each message every time the MAC is checked or, if a message has been changed, a fresh MAC has to be calculated. To avoid this, a separate MAC is calculated for each message and stored in the directory, and a global MAC is calculated for the individual MAC's (treating them as if they were a message) and stored in a secure register. To check a stored message, the global MAC is recalculated (thus verifying the MAC of the message), and the MAC of the message is recalculated (thus verifying the message). If the message is changed, its new MAC and a new global MAC are calculated. The system can be extended to a hierarchy of sub-global MAC's.

Abstract: A secure communication system wherein encrypted messages are passed between selected pairs of user terminals in a secure messaging system. A link is first established between the two terminals of the pair, one terminal sending a request to a key distribution center (KDC), which then provides encrypting keys to both terminals so they can communicate with each other. (Messages involving the KDC are themselves protected by encryption). The keys sent out by the KDC are key transporting keys, which are used by the terminals solely to transport data transporting keys between each other. The data transporting keys are used to transport (encrypt) the actual messages, and for security are changed after a usage count is reached; a fresh data transporting key is then generated and transferred under the key transporting key. This minimizes the load on the KDC. A hierarchy or key transporting keys can be used. The KDC (but not the user terminals) maintains a log to enable recover after a system failure.

Abstract: A secure messaging system with several terminals and many system (control) messages transmitted between the various terminals. These messages can deliberate, accidentally change sequence, or be deleted or duplicated. To protect the system against this, an acknowledgement is sent for every message received (except a simple acknowledgement), and each station stores copies of the messages it has sent, deleting them only when acknowledged. When a new message is to be sent or a non-receipt of acknowledgement time-out occurs, a packet is sent with all previous messages in store prefixed to the new message, so the receiving station cannot act on the new message before receiving and acting on the previous messages. There are known means for ignoring duplicated messages. Preferably there is chained serial authentication of the messages in the packet so that even if one is garbled, they can be acted on up to that point.