International Association for Cryptologic Research
In this paper the authors investigated the use of Instantaneous Frequency (IF) instead of power amplitude and power spectrum in side-channel analysis. By opposition to the constant frequency used in fourier transform, instantaneous frequency reflects local phase differences and allows detecting frequency variations. These variations reflect the processed binary data and are hence crypt-analytically useful. IF exploits the fact that after higher power drops more time is required to restore power back to its nominal value.