In this paper, an original technique for fast low-complexity PN code acquisition is proposed. Its major advantage is that the receiver does not need to know the PN code itself, but only its length. We have applied the proposed technique in the context of GNSS receivers, and more specifically to Galileo, the European contribution to GNSS. The analysis of its performance shows that the proposed technique significantly accelerates the signal acquisition process since it greatly reduces the search space. Moreover, its architecture has a low cost implementation.