Which of the following is the most secure form of triple-DES encryption?

A.
DES-EDE3

B.
DES-EDE1

C.
DES-EEE4

D.
DES-EDE2

Explanation:
The reason is that it uses three keys. Four keys cannot be used. The other alternatives do not use as
many keys so less secure. We do not believe there is such a thing as DES-EDE1, but it would still be
less secure if it would exist.