Hi Friedrich, The way it is defined in the code is consistent with the paper mentioned in the documentation (H. Heys paper on tutorial of differential and linear cryptanalysis) which, I believe, is used by many cryptanalysis researchers or students to learn differential and linear cryptanalysis for the first time. Together with the paper, SageMath can be a companion educational tool for introducing the concept of linear and differential cryptanalysis. In that respect i think its more beneficial to change its description in the documentation rather than changing the function.
Regards, Rusydi On 16-02-18 15:55, Friedrich Wiemer wrote: > I recently stumbled across the fact that the implementation of > SBox().linear_approximation_matrix() returns /scaled/ Fourier > coefficients. > While the documentation says exactly this, i.e., "[the matrix] encodes > the bias[es]", my personal intuition is that this matrix should > contain the actual Fourier coefficients. > In fact, the matrix is computed using the Fourier-Walsh transform for > each component function and then scales the resulting matrix > accordingly. On the other side, this scaling is then for other methods > reversed (e.g. in the `nonlinearity` and `linearity` method). > > Of course, my argument is basically only personal taste, but my > feeling is that containing the /unscaled/ Fourier coefficients is, > what one would assume when only looking at the API and not at the > documentation. > So, I propose to change this, but would like to hear your opinions on > this? > -- > You received this message because you are subscribed to the Google > Groups "sage-devel" group. > To unsubscribe from this group and stop receiving emails from it, send > an email to sage-devel+unsubscr...@googlegroups.com > <mailto:sage-devel+unsubscr...@googlegroups.com>. > To post to this group, send email to sage-devel@googlegroups.com > <mailto:sage-devel@googlegroups.com>. > Visit this group at https://groups.google.com/group/sage-devel. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
