A system and method for determining whether a cryptographic system is being observed for power consumption analysis in an attempt to decipher secret keys. The system comprises a first external connection to receive an input voltage, an internal voltage regulator with an external capacitor to produce the desired voltage for the cryptographic system. The internal voltage regulator typically includes a switch that passes current from the first external connection to the external capacitor. By monitoring the frequency at which the switch is activated, it is possible to detect that an external voltage is being applied to the external capacitor. This external voltage is typically used to perform SPA or DPA operations. Thus, the cryptographic system may cease performing any encryption or decryption operations if an external voltage is detected.