Randomization of Message Contents With and Without Encryption for Covert Communication Scenarios

Steganographic methods often presuppose that the concealed message appears random or undergoes encryption. When confidentiality is a concern, encryption results in a random message, yet the exchange of keys can pose challenges and compromise clandestine communication. In situations where robust encryption is not imperative, the inquiry arises whether alternative cryptographic techniques, which are less costly than encryption, can yield equivalent levels of randomness. This will help computationally weak devices such as IoT sensors. This paper studies both research problems. Initially, we present a methodology inspired by blockchain proof-of-work to securely transmit the key alongside the encrypted message, circumventing the need for a preceding key exchange. Subsequently, we introduce frameworks utilizing cryptographic hash functions and T-functions to supplant symmetric encryption algorithms in counter mode, while also exploring lossless compression as a mechanism for achieving randomness. We outline potential scenarios where either the covert receiver or sender can undertake the proof-of-work to ensure the sender's confidentiality or authenticity. We implement all devised schemes and subject them to rigorous testing using DIEHARD and NIST STS test suites. The results obtained validate the viability of the proposed methodologies.