A method of decoding soft input information related to a transmitted word of a linear block code (n, k) and providing hard or soft output information is disclosed. The method comprises the steps of forming a reliability vector from the input information, identifying (n−k) linearly independent least reliable symbols and k most reliable symbols, converting a parity check matrix of the linear block code to a pseudo-systematic form with respect to the least reliable symbols, calculating extrinsic information and composite information for the most reliable symbols using the soft input information and the pseudo-systematic parity check matrix, and calculating extrinsic information for the least reliable systems using composite information for the most reliable symbols.