This paper suggests that a watermarking technique based on the number theoretic transform (NTT) may effectively be employed for detecting alterations on lossless digital master images. Due to its fragility, the NTT-based technique is sensitive to detecting alterations, compared with that based on the discrete Fourier transform (DFT).

We propose an asymmetric fragile watermarking technique that uses a number theoretic transform (NTT). Signature data is extracted from a watermarked image by determining correlation functions that are computed using the NTT. The effectiveness of the proposed method is evaluated by simulated detection of altering.