The invention provides a method of encoding a binary data message for transmission over a data network. The method comprises allocating consecutive six bit sequences from the binary data message to consecutive respective bytes of an encoded data message; adding a predetermined bias value to some or all of the byte values of the encoded data message; and replacing respective selected data byte values in the encoded data message with one or more corresponding replacement data byte values. The invention further provides a method that comprises forming two or more message fragments from the binary message, each message fragment comprising respective bit sequences of the binary message; encoding each message fragment by the method outlined above to form two or more encoded message fragments; and adding a header to each encoded message fragment. The invention further provides an encoding engine for encoding a binary data message for transmission over a data network.