Abstract
SHDM stands for Sphere-Hardening Dither Modulation and is a watermarking algorithm based on quantizing the norm of a vector extracted from the cover work. We show how SHDM can be integrated into a fully commutative watermarking-encryption scheme and investigate implementations in the spatial, DCT, and DWT domain with respect to their fidelity, robustness, capacity, and security of encryption. The watermarking scheme, when applied in the DCT or DWT domain, proves to be very robust against JPEG/JPEG2000 compression. On the other hand, the spatial domain-based approach offers a large capacity. The increased robustness of the watermarking schemes, however, comes at the cost of rather weak encryption primitives, making the proposed CWE scheme suited for low to medium security applications with high robustness requirements.
Highlights
Encryption and watermarking are both important tools in protecting digital contents, e.g., in digital rights management (DRM) systems
The present paper describes a novel commutative watermarking-encryption (CWE) scheme, that couples sign-bit encryption of selected pixel grey values or transform coefficients as encryption part with Sphere-Hardening Dither Modulation (SHDM) [2, 3] as the watermarking part
7 Conclusion We have presented a novel commutative watermarking encryption (CWE) scheme, which is very robust to common attacks like Joint photographic expert group (JPEG)/JPEG2000 compression and noise addition, especially when implemented in some transform domain (Discrete-Cosine or Discrete-Wavelet)
Summary
Encryption and watermarking are both important tools in protecting digital contents, e.g., in digital rights management (DRM) systems. The least significant bitplane is replaced by the signs of the plaintext coefficients In this approach, using a secret transform domain increases the security of the scheme, albeit at the cost that encryption and watermarking are not completely independent, but need to share a common secret. Another approach to commutative watermarking is provided by deploying homomorphic encryption techniques so that some basic algebraic operations such as addition and multiplication on the plaintexts can be transferred onto the corresponding ciphertexts, i.e., they are transparent to encryption [1, Sec. 2.1].
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