A computer program obfuscating system including a processor to provide a computer program including at least one computer program variable, and add an opaque predicate to the computer program to obfuscate the computer program so that the opaque predicate added to the computer program comprises at least one polynomial including a polynomial P, during execution of the obfuscated computer program, the polynomial P is evaluated yielding at least one result including a first result R1, and during execution of the obfuscated computer program, the opaque predicate is evaluated based on the at least one result R1 such that a decision as to whether or not to perform the first command is dependent upon comparing the first result R1 to at least one value in accordance with a predetermined mathematical relationship. Related apparatus and methods are also included.