1. A signature generation apparatus comprising: a plurality of basic operation execution units each executing a basic operation included in a signature generation procedure; and a whole operation control controller connected to the plurality of basic operation execution units to control operations in the basic operation execution units and monitor operation states of the basic operation execution units, wherein when there is a basic operation execution unit among the plurality of basic operation execution units which is executing a secret operation which uses data to be concealed as an argument, the whole operation controller causes other basic operation execution units than the basic operation execution unit to simultaneously execute a random number operation which uses a random number as an argument.