$DE{S}_k(x)=y=>DE{S}_{\frac{?}{\text{b}\text{a}\text{r}}(k)}(\stackrel{}{x})\frac{?}{b}=ar(y)$

for every key $k$ and input $x,$ where $\frac{?}{\text{b}\text{a}\text{r}}(z)$ denotes the bitwise complement of $z.$ This is

called the complementarity property of DES. Does this represent a serious vulnera$-$

bility in the use of triple$-$DES as a pseudorandom permutation? Explain.