Covert Transmission via Steganography and Smart Contract

The Internet of Things (IoT) system collects data from various smart devices and sensors to make tailored decisions. However, in complex IoT setups, privacy can be compromised through data collection, processing, and sharing. Thus, safeguarding data during transmission is crucial. Combining blockchain technology with covert communication has made progress in addressing these issues, but challenges like low data embedding rates and identifiable blockchain transactions with covert data remain. To tackle this, this paper analyzes Ethereum transaction field formats, identifying the input data field as the target for high-capacity embedding. A data covert transmission scheme using hybrid embedding in contract fields is proposed, employing LSB steganography to embed covert data in images and incorporating the image URL into the input data field of Ethereum smart contracts, increasing embedding rates. Additionally, a new method for data embedding based on contract relationships is introduced, enabling covert data transmission through the invocation relationships of smart contracts, rather than directly embedding data in transactions. This makes transactions theoretically indistinguishable from regular ones, enhancing security. Finally, evaluations of undetectability, embedding rate, and scalability show that the proposed schemes excel in all three areas.