As far I know, the Serpent cipher is the only cipher that uses legit bit shifts (
<<) along with circular left shift (
<<<) (correct me if I am wrong).
I have two questions on it:
What security advantage added by bit shift? Why is it used in the first place?
Does the bit shift add vulnerability in differential power attack?
As for the second point: a bit shift adds more zeros, resulting in an unbalanced bit distribution (Hamming weight biases).