Ciphertext-domain fragile watermarking using hamming codes for dual-stage tamper detection and recovery

Cloud storage greatly facilitates large-scale image hosting but also exposes encrypted content to the risk of visually plausible ciphertext-domain tampering after decryption. Such a threat is particularly critical in secure cloud-based image storage and forensics, where the integrity of encrypted visual data must be reliably verified. To address this threat, we propose a dual-stage ciphertext-domain self-embedding fragile watermarking scheme based on Hamming codes, which enables lightweight user-side operation requiring only encryption. Specifically, the user encrypts the plaintext image with any secure algorithm and uploads the ciphertext to the cloud. Without decrypting, the cloud performs a two-stage Permutation Ordered Binary (POB) reversible compression, releasing about 4 bpp of embedding space while maintaining perfect reversibility. In this space, two types of watermarks are embedded: (i) distributed (7,4) Hamming-code-based parity bits across interleaved blocks for bit-level tamper localization and single-bit correction; and (ii) a keyed hash-assisted block authentication watermark (4 bits per $$2\times 2$$ block) for coarse-grained integrity verification. During detection, an adaptive mask-selection mechanism compares the reliability of pixel-level and block-level results and triggers a hybrid image recovery (IHR) process: sparse errors are corrected by Hamming decoding, whereas multi-bit conflicts are refined through prediction-based pixel recovery. Experimental results show that the proposed method outperforms existing schemes in both detection accuracy and reconstruction quality, achieving lossless recovery at $$\gamma =6.25\%$$ and improving PSNR by 7 to 12 dB over the representative ciphertext-domain watermarking method under moderate cropping attacks ($$\gamma =25\%$$).