Reading the challenge description we probably need to figure out the key.
We are given a file called top.v.
Looking at its source code we see that it ends with a compare statement that has to be true:
// I have the feeling "lock" should be 1'b1
assign lock = tmp4 == 64'h5443474D489DFDD3;
We can write a small python script that reverses each step from bottom to top to get the key:
hex_value = 0x5443474D489DFDD3
temp4 = int(hex_value)
temp3 = temp4 + 12345678
# XOR temp3 with "HACKERS!"
temp2 = temp3 ^ 0x4841434B45525321
temp1 = temp2 >> 5
# print hex value of temp1
print(hex(temp1))
After running the script we obtain the correct key: