# Symmetric and Asymmetric indistinguishabilty experiment

In each of those experiments, we have a function $$Gen(x)$$ who generates the key or a pair of keys respectively for symmetric or asymmetric algorithms. $$x = 1^n$$ : I read on other questions that is a $$1$$ string bit of length $$n$$, but I didnìt understood why it is used value as input to generate the key.