In this paper we propose an on-line fault detection architecture for bijective Substitution Boxes used in cryptographic circuits. Concurrent fault detection is important not only to protect the encryption/decryption process from random and production faults, it also protects the system against side-channel attacks, in particular those based on fault injection. We will prove that our solution is very effective while keeping the area overhead very low. Besides, we will analyze the correlation between the information processed by the circuit and the power consumption in order to asses the quality of the solution with respect to other side channel attacks such as Power Analysis techniques.