This document discusses and compares different methods for authenticating digital images, including cryptographic authentication, robust image hashing authentication, and watermarking authentication. Cryptographic authentication uses encryption and decryption but has limitations in localization. Robust image hashing is based on rotation-invariant moments but struggles with large area cropping. Watermarking authentication allows for embedding watermarks for identification and tamper detection but cannot precisely locate tampered regions. Overall, the document concludes that watermarking schemes constructed using chaotic maps provide better security compared to other methods due to chaotic maps' sensitivity to initial conditions.