Encryption vs compression detection

[dila]

I pasted the code here https://pastebin.com/q2Ppk51Q. The ZIP attachment is large because it contains a PDF describing a method of testing random sequences using the WHT.

If you want to know more about the transform, you can read about it in The Design of Rijndael book (PDF available here). Here they give some identities of the function, such as how bitwise XOR of two functions in the Boolean domain corresponds to convolution of their coefficients in the spectral domain.