Abstract: A system and method for developing a software program containing sensitive information requires the use of a developer key (a unique public/private key pair) to download the software onto a uniquely identified developer chip. The software program can then be developed and debugged on the developer chip. After being developed and debugged, the software program is transferred to a uniquely identified release chip for subsequent use. Specifically, transfer of the software program requires use of a release key (also a public/private key pair) that is different from the developer key. The private key part of the developer key, as well as all developer chips (albeit a limited number) are protected by strict security procedures.

Abstract: A system for backing up files from disk volumes on multiple nodes of a computer network to a common random-access backup storage means. As part of the backup process, duplicate files (or portions of files) may be identified across nodes, so that only a single copy of the contents of the duplicate files (or portions thereof) is stored in the backup storage means. For each backup operation after the initial backup on a particular volume, only those files which have changed since the previous backup are actually read from the volume and stored on the backup storage means. In addition, differences between a file and its version in the previous backup may be computed so that only the changes to the file need to be written on the backup storage means. All of these enhancements significantly reduce both the amount of storage and the amount of network bandwidth required for performing the backup.

Abstract: A system for backing up data from a computer disk volume at very high speed by saving a logical image copy of the volume to a backup medium such as magnetic tape. This logical image copy can later be restored in its entirety to a disk volume with a different physical geometry and flaw map in a disaster recovery mode, significantly reducing the time required for such disaster recovery compared to other backup techniques. In addition, the logical image copy on the backup medium also allows selective file restore with performance comparable to that achievable using traditional file-by-file backup/restore methods. The backup process can thus run considerably faster than conventional approaches without sacrificing the restore flexibility normally associated with those approaches.

Abstract: A system for backing up files from disk volumes on multiple nodes of a computer network to a common random-access backup storage means. As part of the backup process, duplicate files (or portions of files) may be identified across nodes, so that only a single copy of the contents of the duplicate files (or portions thereof) is stored in the backup storage means. For each backup operation after the initial backup on a particular volume, only those files which have changed since the previous backup are actually read from the volume and stored on the backup storage means. In addition, differences between a file and its version in the previous backup may be computed so that only the changes to the file need to be written on the backup storage means. All of these enhancements significantly reduce both the amount of storage and the amount of network bandwidth required for performing the backup.

Abstract: An apparatus and method for converting an input data character stream into a variable length encoded data stream in a data compression system. A sliding window data compression algorithm is combined with Huffman encoding on the strings and raw bytes. The Huffman table, in a compressed form, is prepended to the encoded output data. The Huffman codes representing the shortest strings encode both the string length and part of the string offset. Assigning Huffman codes to represent the combined length and offset allows the use of a smaller sliding window size without sacrificing compression ratio. The smaller window size allows implementations in software and hardware to minimize memory usage, thus reducing cost.

Abstract: An apparatus and method are disclosed for converting an input data character stream into a variable length encoded data stream in a data compression system. The data compression system includes a history array. The history array has a plurality of entries and each entry of the history array is for storing a portion of the input data stream. The method for converting the input data character stream includes the following steps. Performing a search in a history array for the longest data string which matches the input data string. If the matching data string is found within the history buffer, the next step includes encoding the longest matching data string found by appending to the encoded data stream a tag indicating the longest matching data string was found and a string substitution code.

Abstract: An apparatus and method are disclosed for converting an input data character stream into a variable length encoded data stream in a data compression system. The data compression system includes a history array. The history array has a plurality of entries and each entry of the history array is for storing a portion of the input data stream. The method for converting the input data character stream includes the following steps. Performing a search in a history array for the longest data string which matches the input data string. If the matching data string is found within the history buffer, the next step includes encoding the longest matching data string found by appending to the encoded data stream a tag indicating the longest matching data string was found and a string substitution code.

Abstract: An apparatus and method are disclosed for converting an input data character stream into a variable length encoded data stream and encoding the variable length encoded date stream according to byte length. A 2 byte length is encoded by 2 bits having the values "00". Encoded lengths of 3 and 4 bytes are represented respectively by 2 bits having the values "01" and "10". Byte lengths of 5 to 7 are represented by 4 bits "1100" to "1110" and so on to thereby enable an efficient procedure for encoding the length of a bit string during compression.

Abstract: A data compression device driver compresses and decompresses files on a disk drive in a computer system when a user copies files from a drive letter assigned to the disk drive to a drive letter assigned to the data compression device driver. Drive parameter blocks for the disk drive and for the data compression device driver contain the assigned drive letter, disk geometry information, a rebuild flag, and a pointer to the device driver. A swapping means swaps the device driver pointers in the drive parameter blocks corresponding to the disk drive and the data compression device driver. From then on, compressed data files may be accessed transparently by using the drive letter which was originally assigned to the disk drive before swapping, which now refers to the data compression device driver.

Abstract: An apparatus and method are disclosed for converting an input data character stream into a variable length encoded data stream in a data compression system. The data compression system includes a history array. The history array has a plurality of entries and each entry of the history array is for storing a portion of the input data stream. The method for converting the input data character stream includes the following steps. Performing a search in a history array for the longest data string which matches the input data string. If the matching data string is found within the history buffer, the next step includes encoding the longest matching data string found by appending to the encoded data stream a tag indicating the longest matching data string was found and a string substitution code.

Abstract: An apparatus and method as disclosed for converting an input data character stream into a variable length encoded data stream in a data compression system. The data compression system includes a history array means. The history array means has a plurality of entries and each entry of the history array means is for storing a portion of the input data stream. The method for converting the input data character stream includes the following steps. Performing a search in a history array means for the longest data string which matches the input data string. If the matching data string is found within the history buffer means, the next step includes encoding the longest matching data string found by appending to the encoded data stream a tag indicating the longest matching data string was found and a string substitution code.

Abstract: An apparatus and method for converting an input data character stream into a variable length encoded data stream in a data compression system. The data compression system includes a history array means. The history array means has a plurality of entries and each entry of the history array means is for storing a portion of the input data stream. The method for converting the input data character stream includes the following steps. Performing a search in a history array means for the longest data string which matches the input data string. If the matching data string is found within the history buffer means, the next step includes encoding the longest matching data string found by appending to the encoded data stream a tag indicating the longest matching data string was found and a string substitution code.

Abstract: An apparatus and method are disclosed for converting an input data character stream into a variable length encoded data stream in a data compression system. The data compression system includes a shift register means. The shift register means has a plurality of entries and each entry of the shift register means is for storing a data character of the input data stream. The method for converting the input data character stream includes the following steps. Performing a search in the shift register means for a data string which matches the input data string. The step for performing the search includes the steps of broadcasting each input data character of the input data stream to each entry of the shift register means and comparing each input data character simultaneously with the previously stored contents of each entry of said shift register means.

Abstract: An apparatus and/or method for generating parity digits of digital information (data) in a digital communication system is disclosed. The communication system (8) is for transferring a plurality of data intervals from an originating data source (12) to a data sink (13). Each data interval comprises one or more blocks of data and each block contains one or more bytes of data. The communication system (8) includes a temporary storage means (24) for holding the data for a limited period. Included are means for transferring (14, 40) one or more data intervals from the data source (12) to the temporary storage means (24) and means for transferring (22, 40) one of the data intervals from the temporary storage means (24) to the data sink (13) including means for calculating (72) error correcting code words associated with each data interval and means for storing (16) the error correcting code words for further processing.

Abstract: An apparatus and/or method for generating a digital clock signal which is frequency and phase referenced to an external digital data signal is disclosed. The external digital data signal is typically subject to variations in data frequency and high frequency jitter unrelated to changes in the data frequency.

Abstract: Disclosed is a digital ultrasonic instrument for measuring the corneal thickness (often referred to as a pachymeter) and for measuring the axial length of the eye (often referred to as a biometric ruler). A number representing corneal thickness or axial length is displayed digitally on a liquid crystal display. The pachymeter incorporates a 20 MHz solid phase piezoelectric transducer, a microprocessor, a gate array, a hybrid analog receiver circuit, a liquid crystal display and four batteries. When axial length is measured, the instrument operates as a biometric ruler, a 10 MHz transducer is used and the software in the microprocessor is modified. Ultrasonic echoes generated by the transducer and various interfaces in the eye are sampled at the rate of 40 MHz which results in equal or greater sensitivity, resolution and accuracy as compared to other pachymeters and biometric rulers currently available.