Patent ID: 6922778
Filing Date: 2005-07-26
Classification: H03M,H04L,H04N

Abstract:
1. A method of transcoding a data message, comprising a plurality of data fields and an authentication code, to produce a transcoded message for transmission to a destination device, the data message being received from a source device wherein said data fields have been coded in accordance with a first coding system, whereby respective data field codes are generated for said data fields and a message code is derived from said data field codes, and wherein said message code has been coded in accordance with a second coding system to generate said authentication code, the method comprising: determining for each data field of the received data message whether to maintain, modify or omit that field; for a field to be maintained, maintaining that field in said transcoded message; for a field to be omitted, coding the field in accordance with said first coding system to generate an omitted field code dependent upon the data field code for that field, and replacing that field by said omitted field code in the transcoded message; for a field to be modified, coding that field in accordance with said first coding system to generate a modified field code dependent upon the data field code for that field, and replacing that field by a modified field, comprising modified data and said modified field code, in the transcoded message; and including said authentication code in the transcoded message.