In this paper, a chipless solution dedicated to the authentication of manufactured products is proposed. The proposed technique is an extension of chipless radio frequency identification (RFID) with the prevention of tags’ cloning due to the use of natural randomness in the fabrication process. or the first time, we proposed a methodology to characterize the chipless RFID tags for the purpose of authentication. The proposed method has a high level of security due to the employment of a database of authenticity. With a nonintrusive and nondestructive operation, the proposed method has promising possibilities for authentication applications, for example, the chipless tags can be inserted (or hidden) in the product packaging. The chipless tags are realized two times intermittently, where each realization is constituted of 45 tags. These two different realizations share the same company, same technology but different film mask to ensure the natural dimensional randomness. The similarity analysis is conducted inside each realization and also between two different realizations. With the help of this technique, it is possible to authenticate two chipless RFID tags exhibiting natural dimensional variations in their designs with a low probability of error.