Nearly Reversible Data Hiding for Encrypted Audios by Modified Histogram Shifting

A nearly reversible and high capacity data hiding mechanism on encrypted audios is proposed in this thesis. In the first phase, instead of vacating room for embedding additional data from the encrypted audios, which may lead to inferior qualities of recovered signals, we exploit the continuity of original audio to estimate half of the samples and embed bits into their estimating errors. A content owner can encrypt the estimating errors with a specific encryption scheme. Note that any one of the existing encryption schemes, such as AES or bitwise exclusive OR, is allowed to be applied to the rest half of samples. With the data hiding key, a data hider can embed data in the encryption version of the audio. At the receiver side, those who have no knowledge about the encryption key are able to extract concealing bits without errors. Moreover, the order of signal decryption and data extraction can be exchanged depending on the requirements of applications. Furthermore, experimental results demonstrate that the proposed work achieved a superior imperceptibility of marked audios with large amount of embedding data and, more importantly, the recovered audios are also nearly totally reversible with segSNR higher than or equal to 60 dB.