Here, the side-channel attack (SCA)-resistant cryptographic chip: a cryptographic circuit employs a voltage scaling technique is studied with hardware Trojan attacks. Two different types of hardware Trojans, sequential hardware Trojan and combinational hardware Trojan, are proposed to be embedded into the SCA-resistant cryptographic chip for leaking the secret key. Moreover, the sequential Trojan can only disclose a single bit of the secret key at a time, while the combinational Trojan is able to leak the whole bit of the secret key at once. As demonstrated in the results, only analysing ∼270 (150) power traces are sufficient to disclose the 8-bit secret key of the sequential (combinational) Trojan-infected chip to the adversary. Furthermore, both the sequential and combinational Trojan-infected chips can evade the testing of the power attack and be detected with the proposed statistical models successfully.