Methods and devices against side-channel analysis

A circuit, comprising:

• a
• hardware processor configured to:
• securely execute an operation in which a first input data is combined with a second input data;
• generate a first input set including the first input data, each data in the first input set being obtained by applying Exclusive OR (XOR) operations to the first input data and to one of first mask parameters in a first mask set;
• generate a second mask set including second mask parameters, each first mask parameter in the first mask set forming a respective mask pair with a corresponding second mask parameter in the second mask set, the mask pairs being such that combinations by XOR operations of the first mask parameter with the second mask parameter in each mask pair produce a third mask set including third mask parameters, the mask parameters in each of the first, second and third mask sets being such that each mask parameter in the mask set includes at least one word, the words in the mask set having a same size and forming a word subset including a single word from each mask parameter of the mask set and a same number of occurrences of all possible values of the words;
• generate a second input set including the second input data, each data in the second input set being obtained by applying XOR operations to the second input data and to one of second mask parameters in a second mask set, each data in the first input set being associated with a respective data in the second input set in a respective input pair, such that the mask parameters from which each data in each input pair is computed are associated by one of the mask pairs;
• compute output data of an output set by applying the operation to each of the input pairs;
• and
• providing the output set as a result of the operation.

A computer program product loaded into a computer memory and comprising code portions which when executed by a computer configure the computer to carry out a method for securely executing an operation combining a first input data with a second input data, the method comprising:

• generating a first input set including the first input data, each data in the first input set being obtained by applying Exclusive OR (XOR) operations to the first input data and to one of first mask parameters in a first mask set,
• generating a second mask set including second mask parameters, each first mask parameter in the first mask set forming a respective mask pair with a corresponding second mask parameter in the second mask set, the mask pairs being such that combinations by XOR operations of the first mask parameter with the second mask parameter in each mask pair produce a third mask set including third mask parameters, the mask parameters in each of the first, second and third mask sets being such that each mask parameter in the mask set includes at least one word, the words in the mask set having a same size and forming a word subset including a single word from each mask parameter of the mask set and a same number of occurrences of all possible values of the words;
• generating a second input set including the second input data, each data in the second input set being obtained by applying XOR operations to the second input data and to one of second mask parameters in a second mask set, each data in the first input set being associated with a respective data in the second input set in a respective input pair, such that the mask parameters from which each data in each input pair is computed are associated by one of the mask pairs;
• computing output data of an output set by applying the operation to each of the input pairs;
• and
• providing the output set as a result of the operation.