Improvement to CDF grounded lattice codes

Abstract

Lattice codes have been evaluated in the watermarking literature based on their behavior in the presence of additive noise. In contrast with spread spectrum methods, the host image does not interfere with the watermark. Such evaluation is appropriate to simulate the effects of operations like compression, which are effectively noise-like for lattice codes. Lattice codes do not perform nearly as well when processing that fundamentally alters the characteristics of the host image is applied. One type of modification that is particularly detrimental to lattice codes involves changing the amplitude of the host. In a previous paper on the subject, we describe a modification to lattice codes that makes them invariant to a large class of amplitude modifications; those that are order preserving. However, we have shown that in its pure form the modification leads to problems with embedding distortion and noise immunity that are image dependent. In the current work we discuss an improved method for handling the aforementioned problem. Specifically, the set of quantization bins that is used for the lattice code is governed by a finite state machine. The finite state machine approach to quantization bin assignment requires side information in order for the quantizers to be recovered exactly. Our paper describes in detail two methods for recovery when such an approach is used.

Difference angle quantization index modulation scheme for image watermarking

“…In recent years, many schemes such as the use of pilot signals [5][6][7], the design of amplitude scale invariant codes [8][9][10]16] and the AQIM method [1,13] have been proposed to tackle this problem. Among all the above mentioned methods, the AQIM method [1] is the most simple and effective watermarking scheme that can resist the gain Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/image attacks.…”

Amplitude Scale Estimation for Quantization-Based Watermarking

“…Several techniques are known in the literature for combating amplitude scale attacks. One of the approaches is based on designing watermarking codes that are invariant to amplitude scale operations, such as modified trellis codes [6], order-preserving lattice codes [7], and rational dither modulation [8]. Another approach is based on estimating the nonadditive operations and inverting them prior to watermark decoding, using pilot signals [9] or blind estimation [10]- [12].…”

“…The method proposed in [11] performs well for low WNR but lacks security, in the sense that an attacker knowing the distortion of the embedder is able to estimate the scaling factors and decode the watermark. The methods based on invariant codes give small probability of error with respect to amplitude scale attacks at the expense of increased probability of error [8], [7] with respect to additive noise attacks and reduced payload [6].…”