Abstract: A processing arrangement of a data communication apparatus is arranged to derive an ordered plurality of modulo-2 summations of respective selections of data bits of a binary data set. The data communication apparatus may either be transmitting apparatus with the processing arrangement serving to determine a target syndrome for subsequent use in error correction, or receiving apparatus with the data processing arrangement being arranged to effect error correction of received data. The processing arrangement effects its selections of bits from the binary data set in accordance with the interconnection of nodes in a logical network of nodes and edges that together define at least a continuum of cells covering a finite toroid. The structuring provided to bit selection by this continuum can be offset by randomness provided by other structures of the network and by the random association of bits of the binary data set with the nodes of the continuum.