Apparatus and method for encoding and decoding attribute data into error

Abstract

Apparatus and methods for encoding information of one class into the parity for main data of another class. One such method and apparatus fundamentally takes one member A.sub.x of a limited first class of data called attribute data and concatenates it with main data. Parity is then calculated on the concatenate word. After the main data and parity is transmitted or recorded, the selected member of the first class of data may be recovered by comparing the received parity to the parity P' generated on the receiver side using the main data and each member of the first class of data to generate a plurality of syndromes. The first all zero syndrome identifies the member of the first class which was encoded into the parity of the main data. Another method and apparatus are similar except that the transmitter side calculates parity P.sub.ax for the selected member of the first class and then encodes that parity into the parity calculated for the main data. On the receiver side, parity bits are calculated for each member of the first class and then combined with parity P.sub.d ' calculated on the main data to generate parity P'. This parity P' is then compared to the received parity P', and the first match indicates which member of the first class was encoded on the transmitter side.