Transition between masked representations of a value during cryptographic calculations

at a method for transition from a first masked representation a value to be kept secret to a second masked representation of the value is according to a first aspect of the invention, at least a precalculated table having a plurality of entries used, and the calculation is carried out as a function of at least one concealment parameters a spying the value to be kept secret to prevent. According to a second aspect the invention is used at least one comparison table the for each table index, the result of a comparison between a of the table index, the result of a comparison between a dependent on the table index Value and a value depending on at least one masking Value indicates. A computer program product and an apparatus comprise corresponding features. The invention provides a technique for spying protected transition between masked representations a value based on different masking rules.