I am trying to design the s-box for AES. Quoting from Wikipedia, the algorithm for applying affine transformation in AES s-box calculation is
Let s (an 8-bit unsigned variable) be the input number.
Let result be 0.
For 5 times:
XOR result with s.
Rotate s one bit to the left.
My question is why the multiplication is done this way? Why only 5 steps?