Now inverse DTFT for the cross co-relation between sequences x[n] and h[n] can be written as :

Put m=0,  then

i.e dot product of sequences x[n] and h[n] = dot product of DTFT's  of  x[n] and h[n] .

in particular put x[n] =h[n] ,  then

The above is Parseval's relation for discrete time periodic signals .