Abstract: A block of user data is formatted by arranging the user data block into a byte array having plural rows and plural columns of bytes. An error correction code is applied to individual ones of the rows of bytes, such that each row has four code words.

Abstract: A data processing apparatus comprises an integrated circuit containing a data processor and a non-volatile store storing at least one security code. A first memory external to the integrated circuit stores data, the data being cryptographically protected in a first format. A second memory external to the integrated circuit is provided for storing data. The apparatus is arranged to transfer data from the first memory via the integrated circuit to the second memory to be accessed by the data processor from the second memory. The integrated circuit is arranged to validate during the transfer the data read from the first memory using a security code stored in the non-volatile store. If the data is validated, cryptographic protection is applied in a second format to the validated data using a security code stored in the non-volatile store. The protected data is stored in the second memory in the second format.

Abstract: A data processing apparatus comprises a monolithic integrated circuit having a data processor, a non-volatile memory storing at least one security code, and at least one interface at the boundary of the integrated circuit via which communication with the data processor can occur. Processing by the data processor of data received at the at least one interface is controlled by the at least one security code.

Abstract: A method of processing data comprising arranging data into a data group comprising a plurality of sub groups each said subgroup comprising a plurality of columns; for each column, determining at least one checksum data of said column; and for each column, storing the checksum data of that column within at least one said subgroup of the group, other than the subgroup to which said column belongs.

Abstract: A magnetic tape includes plural diagonal tracks, each storing a preamble sequence close to user data such that a transducer for reading the track reads the preamble sequence immediately before reading the user data. The preamble sequence is such that when the track is read by the transducer the preamble sequence has a power sequence with a power spectrum substantially equivalent to the power spectrum of the user data. An AGC circuit responds to the transducer.

Abstract: A data transfer device for transferring data to a removable data storage item. The data transfer device encrypts data to be stored using an encryption key, and additionally encrypts a copy of the encryption key using the encryption key. The data transfer device then stores the encrypted data and the encrypted encryption key to the removable data storage item.

Abstract: A data transfer device for exchanging data between a host device and a removable data storage item, wherein data are encrypted or decrypted by the data transfer device during data exchange, whilst permitting interchange with non-encrypting devices.

Abstract: A block of user data is formatted by arranging the user data block into a byte array having plural rows and plural columns of bytes. An error correction code is applied to individual ones of the rows of bytes, such that each row has four code words.

Abstract: A magnetic tape includes plural diagonal tracks, each storing a preamble sequence close to user data such that a transducer for reading the track reads the preamble sequence immediately before reading the user data. The preamble sequence is such that when the track is read by the transducer the preamble sequence has a power sequence with a power spectrum substantially equivalent to the power spectrum of the user data. An AGC circuit responds to the transducer.

Abstract: A method of encoding a digital data stream for writing to a digital storage (DDS) format tape data storage medium comprises writing a byte stream to a preamble region, immediately preceding a user data region. The byte stream has a power spectrum substantially similar to a power spectrum of the user data region. An automatic gain control circuit responds to the preamble data stream in a substantially similar fashion to its response to the user data stream.

Abstract: A method of encoding a digital data stream for writing to a digital storage (DDS) format tape data storage medium, comprises writing a byte stream to a preamble region, immediately preceding a user data region, said byte stream having a characteristic of having a power spectrum (900) substantially similar to a power spectrum of said user data region. An automatic gain control circuit (504) responds to the preamble data stream in a substantially similar fashion to its response to the user data stream. The disclosure may overcome a problem in read channels detecting prior art DDS-1 to DDS-4 format preamble regions in that an automatic gain control circuit of the read channel responds differently to a cyclical preamble region in the known DDS formats, compared with its response to user data, giving rise to increased bit error rate in a sequence detector device of the read channel.

Abstract: An adaptive filter 24 for filtering a signal comprising first streams interspersed with second streams (for example the A and B tracks of a signal retrieved from a tape storage device) comprises respective stores for storing initial filter coefficients for each type of stream. The corresponding coefficients are loaded for the beginning of each stream. The stored coefficients for each stream may be a standard set, or they may be from the adaption process of one or more previous streams of that type. The coefficients may be taken part way through the adaption process, in a minimum error portion of the stream.