Blockchain-Based Authenticated Stego-Channels and Application to Ethereum

Given their usefulness for evading traceability in networks, it is not surprising that steganographic techniques continue in the modern era and have been looked at through the lens of modern threats and technologies. Among such threats include the linkage of contextual information (associated data) to de-anonymize traffic. Such detection would be fatal to steganographic goals. Cryptographic analyses have expanded to include associated data when analyzing confidentiality and authenticity in channel security; in this work we take a similar approach and extrapolate the security model for steganographic analysis to also account for contextual information. We introduce the security definition of Authenticated Stegotext with Associated Data (ASAD), which captures steganographic properties even when there is contextual information sent alongside the hidden data, and provide a concrete stego-embedding scheme, Authenticated SteGotex with Associated tRansaction Data (ASGARD). Our scheme leverages a blockchain-based channel medium for the transmission of hidden data, namely the Ethereum blockchain. We analyze ASGARD in the ASAD framework and present details on implementation and real-world security considerations.