A system and method for authenticating a radio-frequency identification tags based on the features of the modulation features of the RFID signal. Dynamic wavelet fingerprint features are extracted from the signal by applying a wavelet transform to the signal to determine wavelet coefficients at a plurality of times and frequency scale values, creating a binary image from the wavelet coefficients, and measuring image features of at least one fingerprint object in the binary image. The measured features of the binary image fingerprint objects are compared to a database of features for the signal's EPC to authenticate the RFID tag.