A Covert Communication Method Based on Time Attributes Shifting of Online Video Bullet Comment

The covert communication method, which utilizes video bullet comments, can significantly enhance the interaction between the two parties engaged in social media. However, the current method suffers from inadequate transmission capacity as a result of the restricted payload of an individual bullet comment. To address this issue, a covert communication method based on time attribute shifting of online video bullet comments is proposed. On the sending end, it initially determines the number of loaded bullet comments based on the length of secret information and appropriately distributes these comments across multiple relative time slots within the video. Subsequently, within each slot, reference bullet comments that correspond one by one to the loaded ones are selected from existing bullet comments. The relative and absolute time attributes of the loaded comments are then generated by shifting those of the reference bullet comments according to the secret information to be embedded. The content of the loaded bullet comments is derived from adjacent bullet comments in terms of relative time dimension. On the receiving end, it extracts dual-time attributes from downloaded loaded bullet comments obtained from websites to retrieve reverse secret information. Through experiments, the best safe interval for controlling the time shifting is achieved by employing two evaluation methods, $\epsilon $ -similarity score and Compressibility score. Based on this, experiments are conducted on various video platforms, resulting in a significant increase in the transmission capacity using the proposed method at least 2.50 times.