1. Data processing method, characterized in that it comprises the following steps: determining a first result data word from a first input data word and a first secret data word; obtaining a first compressed data word from the first result data word or the first input data word using a compression algorithm; determining a second result data word from a second input data word and a second secret data word; obtaining a second compressed data word from the second result data word using the compression algorithm; comparing the first compressed data word and the second compressed data word.