is there any other way to solve it, since it is a pdf?

How Secure is AES-128 Against Brute Force Attacks?
AES processes 128 bits of input data at a time. Based on the substitution-permutation network, AES is a symmetric key. AES performs all its computations on bytes which means it treats the 128 bits of a block as 16 bytes. The bytes are processed as a matrix with 16 bytes organized into four columns and four rows. DES with a key size of 56 bits has been cracked using brute force attacks in the past. AES-128 is a 128-bit symmetric key that is computationally secure against brute force attacks.