Given a compact set of real numbers, a random $C^{m+\alpha }$-diffeomorphism is constructed such that the image of any measure concentrated on the set and satisfying a certain condition involving a real number $s$, almost surely has Fourier dimension greater than or equal to $s/(m+\alpha )$. This is used to show that every Borel subset of the real numbers of Hausdorff dimension $s$ is $C^{m+\alpha }$-equivalent to a set of Fourier dimension greater than or equal to $s/(m+\alpha )$. In particular every Borel set is diffeomorphic to a Salem set, and the Fourier dimension is not invariant under $C^m$-diffeomorphisms for any $m$.