Let E subscript k space left parenthesis m right parenthesis denote AES$-128$ encryption of message m with key k$.$ Suppose triple AES$-128($E cubed$)$ is performed by choosing keys k$1$ and k$2$ and computing E cubed subscript k $1$ comma space k $2$ space end subscript equals space E subscript k $1$ space end subscript left parenthesis E subscript k $2$ space end subscript left parenthesis E subscript k $2$ space end subscript left parenthesis m right parenthesis right parenthesis right parenthesis.

Using brute$-$force attack, how many operations does an attacker need to find the encryption keys $?$

Question $2$ Select one:

A$\mathrm{.}2128$

B$\mathrm{.}264$

C$\mathrm{.}2384$

D$.$None

E$\mathrm{.}2256$