If you're complaining because it's faster than O(N*log(N)), the fixed key size guarantees you'll never meet a sufficiently large N which is required when doing big-oh analysis.
If you're complaining because of the k, k is the number of bits in the key and it's perfectly reasonable to have that spelled out explicitly.
If you're complaining because of the k, k is the number of bits in the key and it's perfectly reasonable to have that spelled out explicitly.