Random delays and dynamic frequency switching are widely adopted in smartcards and embedded systems as temporal hiding countermeasures to side channel attack.Temporal hiding is regarded as efficient to enhance the security of cryptographic devices. However, spectral analysis with Fast Fourier Transform is a powerful method to defeat temporal hiding countermeasures. Spectral analysis shares the same merit with integration different power attack. Multi-bit spectral analysis is enhanced with partitioning power analysis, which is much more effective than the correlation power analysis in the spectral domain. Multi-bit spectral analysis effectively defeats temporal hiding countermeasure with floating-mean dynamic frequency switching countermeasure. It is suggested cryptographic devices should employ other countermeasures together with hiding to ensure side channel security.