General Instrument Corporation

Comstream Corporation

Constream Corporation

James N Esserman

Edward A Krause

Itzhak Gurantz

Woo H Paik

Vincent C Liu

Steven E Anderson

Jerrold A Heller

Roy A Griffin, Iii

Shimon Tzukerman

Paul Moroney

Yoav Hebron

Paul Shen

Christopher John Bennett

Fredric Joel Harris

Ron D Katznelson

Sreenivasa A Raghavan

Steven R Hart

Digital data are communicated from a transmitter to a terrestrial receiver by encoding the data into first and second 1/2 rate convolutional encoded signals during different periods. During the different periods, the convolutional signals are encoded into first and second forward error correction convolutional encoded signals having 2/3 and 6/7 punctured codes transmitted to the receiver via a satellite. Power emitted from the satellite during the first period is 3 db lower than that emitted during the second period. An antenna dish having a diameter no greater than about 1 meter is at the receiver responsive to both signals emitted from the satellite. The encoded signals include sequential bits P.sub.1 (0), P.sub.1 (1), etc. and P.sub.2 (0), P.sub.2 (1), etc. At the 2/3 rate, parallel punctured bit streams respectively including sequential bits P.sub.1 (0), P.sub.2 (1), P.sub.2 (2), P.sub.1 (4) and P.sub.2 (0), P.sub.1 (2), P.sub.2 (3), P.sub.2 (4) are derived. At the 6/7 rate, the punctured bit streams are respectively P.sub.1 (0), P.sub.2 (1), P.sub.1 (3), P.sub.1 (5), P.sub.2 (6), P.sub.2 (8), P.sub.2 (10) and P.sub.2 (0), P.sub.2 (2), P.sub.2 (4), P.sub.1 (6), P.sub.2 (7), P.sub.1 (9), P.sub.1 (11). Simultaneously derived bits of the parallel punctured bit streams simultaneously QPSK modulate a carrier. A punctured clock is combined with the serial signal to derive a pair of wavetrains G1 and G2 including the I and Q channel sequential bits and dummy bits inserted into the serial signal. The receiver responds to the QPSK carrier to derive a serial signal having sequential bits so channel I and Q sequential bits I(0), I(1), I(2) etc. and Q(0), Q(1), Q(2) etc. at the same time slots t.sub.k, t.sub.k+1, t.sub.k+2 are sequentially derived as I(0), Q(0), I(1), Q(1), I( 2), Q(2) etc.

Transmitting and receiving apparatus and method including punctured

A variable digital filter employs a variable rate sample clock with combinations of various digital filter elements such as an efficient implementation of decimation to achieve various filter realizations allowing a selectable output bandwidth. More specifically, a digital filter apparatus is coupled to receive input analog signals from a fixed anti-aliasing analog filter and optionally includes one or several stages of digital decimation filters, a low-pass filter, an optional equalizer, and an optional high-pass filter each of which may be programmed so as to configure the device with a variety of transfer characteristics. The filter device employs an input sample clock in the range of F-K*F, where, in a specific embodiment K is selected to be 2. The selectable combination of elements and stages used to form the filter needed is operative at a broad range of sample rates over a predetermined bandwidth range without loss of resolution. An extremely simple digital filter with a bandwidth of 1/4 the input sample rate is also shown.

Variable rate digital filter

A finite field parallel multiplier in GF(q.sup.m) including a router for directing 2m-1 components in m groups of m single-component signal lines towards m computing circuits for performing multiply and add modulo-q. The router guides m components from a first finite field element along with an additional m-1 components generated from linear combinations of the m components of the first finite field element. Each of the computing circuits receives all of the components from the second finite field element and m components provided by one set of signal lines through the router. Each computing circuit generates a single component for the resultant finite field element. These resulting components may be input through a basis change circuit to obtain a result in the desired basis.

Finite field parallel multiplier

Digital still picture signals are processed for compression. A picture signal is divided into successive blocks containing data corresponding to different portions of a still picture. A selected block for the still picture is compared to an area of the picture defined by a plurality of previous blocks to try to locate a set of data in the area that is similar to the selected block. An error signal is generated that indicates the difference between the selected block and the best fit block of previously received data for the picture. Both the error signal and the current block are compressed. The amount of data in the compressed error signal is compared to the amount of data in the compressed current block to determine which provides the least amount of data for communication to a data receiver. An offset vector is appended to each selected error signal to identify the portion of the previously received picture data in which the corresponding best fit block resides. A data receiver recovers the digital still picture data by applying the offset vector for each received compressed error signal to a previously received area of the still picture data to recover the best fit block required to recreate the current data set from the received error signal.

Method and apparatus for compressing digital still picture signals

Compromise of a predetermined secure data processing routine by a procedure known as a 'clock attack' is prevented by a method that inhibits synchronization with externally generated instructions by preventing determination of the time of execution predetermined data processing routine in relation to occurrence of an externally observable event that precedes the execution of the predetermined routine. The method includes the step of (a) randomly varying the duration between the occurrence of the externally observable event and the execution of the predetermined routine. Step (a) includes the steps of (b) executing one or more interim data processing routines between the occurrence of the externally observable event and the execution of the predetermined routine; and (c) randomly varying the duration of said interim routines. Steps (b) and (c) may include the step of (d) randomly assembling m said interim routines for said execution from a group of n stored routines having different durations, wherein m and n are integers, with n being greater than m. Step (d) may include either the step of (e) randomly accessing said m interim routines from a secure memory; or the steps of (f) randomly accessing pointers for said m interim routines from a secure memory; and (g) accessing said m interim routines from a memory in response to said pointers. Step (c) includes the step of (h) randomly varying the duration of the interim routines in response to dynamically processed data that does not repetitively recur each time said interim routines are accessed. The method further includes the steps of (i) monitoring said interim routines to detect whether said interim routines are being tampered with; and (j) preventing the execution of said predetermined routine in response to detecting that said interim routines are being tampered with.

Determination of time of execution of predetermined data processing

A descrambler for descrambling scrambled information signals through use of a predetermined decryption key. The processing means are adapted for processing data in accordance with a number of different data processing routines to descramble said scrambled information signals, including a routine for descrambling said scrambled information signals that utilizes said predetermined decryption key, and a routine for generating said predetermined decryption key. The processing means includes means for responding to an instruction for generating said predetermined decryption key by processing a first signal provided by the processing means with a second signal to generate said predetermined decryption key; and means for providing at least a portion of said second signal for processing with said first signal by retrieving a portion of said stored data from a portion of said memory means identified by a dynamic pointer contained in said instruction for generating said decryption key, with said retrieved data being data that is also used in a said data processing routine other than said routine for generating said predetermined decryption key.

Security enhancement in a data processor through use of dynamic

A secure communication network serves a plurality of terminals grouped into different security categories. Each terminal includes a replaceable security element containing a security algorithm specific to the security category to which the terminal is assigned. Upon the breach of a particular security version, the security elements in the affected category are replaced with new elements containing a different algorithm. The security elements are relatively low cost, and can be replaced on an as needed or periodic basis to maintain system security.

Apparatus and method for upgrading terminals to maintain a secure

Signal encryption apparatus is provided for generating a common key and a distinct key from the same common secret generating key. A generating key is combined with common parameter data to provide a common intermediate key. The common intermediate key is used to produce a common key. The generating key is also combined with distinct parameter data to provide a distinct intermediate key. The distinct intermediate key is used to produce a distinct key. The system has particular applicability to the provision of category and program keys for use in a satellite television scrambling system. The generating key is used to produce the same category key at all uplinks, and different program keys at each uplink.

Signal encryption apparatus for generating common and distinct keys

A field upgradeable security system deciphers signals received from a communication network. An information processor includes a receptacle for receiving a replaceable security element. The replaceable security element generates a working key necessary to the operation of the information processor. The working key is communicated to the information processor encrypted under a secret key. The information processor decrypts the encrypted working key for use in deciphering a received communication signal. Additional layers of encryption can be added to the communications between the information processor and security element to increase the level of security.

Information processing apparatus with replaceable security element

Motion compensated coding of interlaced digital video signals is provided. Pixel data from successive interlaced video fields is compared to similarly situated pixel data in a plurality of previous fields to find a preferred counterpart for each current field set of pixel data. A prediction error signal is generated for each current field set of pixel data indicative of the difference between it and its preferred counterpart from a previous field. Each prediction error signal is encoded with data indicative of the previous field in which the preferred counterpart can be found. In a preferred embodiment, each set of current field pixel data is compared to a range of similarly situated pixels in each of the previous fields, and the prediction error signal is also encoded with motion vector data indicative of the location of the preferred counterpart in its previous field.

Motion compensation for interlaced digital television signals

An image area is refreshed during the transmission of a set of motion compensated sequential video images. The video images are divided into a plurality of adjacent regions. The image area is refreshed during a refresh cycle by communicating a different region in each successive video image of the set without motion compensation. Motion compensation of the previously refreshed regions of the image area during the refresh cycle is restricted to an area containing only the previously refreshed regions. Video image data from a current region being refreshed is encoded for use by a decoder in identifying it as non-motion compensated data.

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San Diego, CA, United States of America

James N Esserman