Abstract: An encrypted program received in an MPEG transport stream is decrypted by receiving an address in the MPEG transport stream, reading a key from a memory in accordance with the received address, and decrypting the encrypted program based on the key.

Abstract: An encrypted program received in an MPEG transport stream is decrypted by receiving a message in the MPEG transport stream, wherein the message contains a key, decrypting the encrypted program based on the key, and replacing the message in the MPEG transport stream with a null packet.

Abstract: In a transmitter, data is encrypted by use of a data key, the data key is encrypted based on a first modification key, and the first modification key is encrypted based on a second modification key such that the first and second modification keys are different keys. The encrypted data, the encrypted data key, and the encrypted first modification key are transmitted to a receiver. In the receiver, the encrypted first modification key, the encrypted data key, and the encrypted data are received from the transmitter. The encrypted first modification key is decrypted based on the second modification key, the encrypted data key is decrypted based on the decrypted first modification key, and the encrypted data is decrypted by use of the decrypted data key.

Abstract: One embodiment involves encrypting an MPEG transport stream by seeding a random number generator with a seed derived from at least a portion of the MPEG transport stream to produce a random number output. At least one program key and at least one modification key are generated from the random number output. At least portions of the MPEG transport stream are encrypted with the program key. At least one stored key is modified according to the modification key to produce a message segment key. The program key and the modification key are encrypted with the message segment key. The encrypted MPEG transport stream, the encrypted program key, and the encrypted modification key are multiplexed to form a multiplexed output.

Abstract: At a transmitter, a program is encrypting according to a one program key, the program key is encrypted, and the encrypted program, the encrypted program key, and non-encrypted PSI data to a receiver are transmitted. At a receiver, the encrypted program, the encrypted program key, and the non-encrypted PSI data are received, the encrypted program key is decrypted, the encrypted program is located according to the non-encrypted PSI data, and the located encrypted program is decrypted according to decrypted program key.

Abstract: The use of keys to encrypt data in a transmitter and to decrypt encrypted data in a receiver are synchronized in accordance with a synchronization signal that opportunistically replaces a null packet in an MPEG transport stream. Additionally or alternatively, key related information is transmitted and/or received in place of a null packet in the MPEG transport stream and is used to encrypt and/or decrypt data transmitted and/or received in the MPEG transport stream.

Abstract: Data is encrypted according to a plurality of data keys. During the encryption of the data, the data keys are rotated according to a data key rotation pattern, and the rotation of the data keys includes repetitive use of the data keys during the encryption of the data. The encrypted data is transmitted to a receiver. Additionally or alternatively, encrypted data is received from a transmitter. The encrypted data is decrypted according to a plurality of data keys. During the decryption of the encrypted data, the data keys are rotated according to a data key rotation pattern, and the rotating of the data keys includes repetitive use of the data keys during the decryption of the encrypted data.

Abstract: Messages are encrypted/decrypted according to a modified triple wrap procedure in which the messages are encrypted/decrypted in three encryption/decryption operations and are processed in three additional operations using first, second, third, fourth, fifth, and sixth keys.

Abstract: In a transmitter, data is encrypted by use of a data key, the data key is encrypted based on a first modification key, and the first modification key is encrypted based on a second modification key such that the first and second modification keys are different keys. The encrypted data, the encrypted data key, and the encrypted first modification key are transmitted to a receiver. In the receiver, the encrypted first modification key, the encrypted data key, and the encrypted data are received from the transmitter. The encrypted first modification key is decrypted based on the second modification key, the encrypted data key is decrypted based on the decrypted first modification key, and the encrypted data is decrypted by use of the decrypted data key.

Abstract: In a transmitter, data is encrypted by use of a data key, the data key is encrypted based on a first modification key, and the first modification key is encrypted based on a second modification key such that the first and second modification keys are different keys. The encrypted data, the encrypted data key, and the encrypted first modification key are transmitted to a receiver. In the receiver, the encrypted first modification key, the encrypted data key, and the encrypted data are received from the transmitter. The encrypted first modification key is decrypted based on the second modification key, the encrypted data key is decrypted based on the decrypted first modification key, and the encrypted data is decrypted by use of the decrypted data key.

Abstract: An encrypted program received in an MPEG transport stream is decrypted by receiving a message in the MPEG transport stream, wherein the message contains a key, decrypting the encrypted program based on the key, and replacing the message in the MPEG transport stream with a null packet.

Abstract: An encrypted program received in an MPEG transport stream is decrypted by receiving an address in the MPEG transport stream, reading a key from a memory in accordance with the received address, and decrypting the encrypted program based on the key.

Abstract: A synchronous data link signal is generated for supply between digital television equipment in a studio and an RF transmitter. The synchronous data link signal includes first data to be encoded at a first data rate, second data to be encoded at a second data rate less than the first data rate, and a map defining the relative amounts and placement of the encoded first and second data in the synchronous data link signal. The first data is in the form of first output data packets of a predetermined size. The second data and the map data are multiplexed so as to provide more than one second output data packet having the predetermined size. The first and second output data packets are then multiplexed so as to provide the synchronous data link signal.

Abstract: A translator demodulates a received digital television signal so as to produce a digital data stream, a symbol clock, and a byte clock, wherein the symbol clock and the byte clock are corrupted by phase noise. The digital data stream is written into a buffer in response to the corrupted byte clock. The corrupted symbol clock is applied to a frequency/phase locked loop having a narrowband loop filter. The frequency/phase locked loop produces a regenerated symbol clock having substantially no phase noise. The digital data stream is read from the buffer in response to the regenerated symbol clock. The digital data stream read from the buffer and the regenerated symbol clock are applied to a modulator for re-broadcasting of the received digital television signal.

Abstract: A synchronous data link signal is generated for supply between digital television equipment in a studio and an RF transmitter. The synchronous data link signal includes first data to be encoded at a first data rate, second data to be encoded at a second data rate less than the first data rate, and a map defining the relative amounts and placement of the encoded first and second data in the synchronous data link signal. The first data is in the form of first output data packets of a predetermined size. The second data and the map data are multiplexed so as to provide more than one second output data packet having the predetermined size. The first and second output data packets are then multiplexed so as to provide the synchronous data link signal.

Abstract: A translator demodulates a received digital television signal so as to produce a digital data stream, a symbol clock, and a byte clock, wherein the symbol clock and the byte clock are corrupted by phase noise. The digital data stream is written into a buffer in response to the corrupted byte clock. The corrupted symbol clock is applied to a frequency/phase locked loop having a narrowband loop filter. The frequency/phase locked loop produces a regenerated symbol clock having substantially no phase noise. The digital data stream is read from the buffer in response to the regenerated symbol clock. The digital data stream read from the buffer and the regenerated symbol clock are applied to a modulator for re-broadcasting of the received digital television signal.

Abstract: An encoder-modulator for coupling a digital baseband television signal to a VSB digital television receiver that includes filters, equalization circuitry, and forward error correction circuitry for correcting signal impairments that are below a given threshold. The encoder-modulator processes the baseband signal for low power transmission on an RF channel with less-than-nominal bandpass characteristics. A coaxial cable or other low noise communication link directly connects the RF signal to the RF input of the television receiver. Any errors or signal impairments in the transmitted signal that are below the predetermined threshold are corrected by the filters and equalization circuitry built into the VSB digital television receiver.

Abstract: An input signal of frequency tolerance A is combined with a reference first signal having a frequency tolerance B to develop a second signal having a combined frequency tolerance of -A and B . The input signal is combined with the second signal to offset and cancel the A and -A frequency tolerances to produce an output signal having a B frequency tolerance.

Abstract: An interface for coupling 19.39 MHz serial packetized transport data in MPEG form to parallel transport data having a maximum symbol rate of 10.76 megasymbols per second. The incoming data includes filler packets to assure that the input bit rate is always in excess of a nominal bit rate. A serial/parallel decoder generates packetized parallel data which is applied to a packet remover. A buffer of multi packet capacity is periodically read to determine its fullness. Packets are removed as required to maintain the desired input bit rate. The buffer supplies a filler packet inserter that is also operated in accordance with the buffer fullness to assure an optimized output packetized data stream of symbols that does not exceed a maximum symbol rate.

Abstract: A convolutional interleaver or deinterleaver comprises an address signal generator for repeatedly generating [(B-1)N/2]+1 sequences of address signals, where B is a desired interleave depth and N is a value equal to or greater than the number of data bytes in a R-S block of the data stream. Each of the sequences corresponds to a respective row of a B column matrix, the first column of which comprises [(B-1)N/2]+1 consecutively numbered values. Each remaining column comprises the preceding column rotated by an integer multiple of N/B. The address signals are applied to a memory having [(B-1)N/2]+1 storage locations for reading the data stored at the address memory location and then writing the current data byte to the same memory location.