$1)$ Encrypt the message "ATTACK AT DAWN" using a $3-$rail fence cipher.

$2)$ Consider a $3$x$2$ Hill Cipher matrix A $=[[2,1,5],[7,4,3],[1,0,2]].$ Encrypt the plaintext "ATTACK" using matrix multiplication.

$3)$ You are tasked with designing a hash function HHH that utilizes bitwise XOR operation. Calculate the hash value of the concatenated string "Hello" $+$ "World" using HHH$.$