Secure and efficient covert communication for blockchain-integrated SAGINs

Blockchain has brought great potential in improving Space-Air-Ground Integrated Networks(SAGINs) in terms of security and efficiency. In blockchain-integrated SAGINs, many applications and services inherently require both the communication contents and communication behaviors to be secure against eavesdroppers, in which a covert communication algorithm is always deployed as a fundamental communication component.However, existing covert communication schemes suffer from critical problems. On the one hand, they require a sender to locally maintain a cryptographic key for a long period of time, which is very costly and inefficient to renew which means renewing the secret key. On the other hand, the ciphertext of covertly sent data would explicitly appear in the network,and thereby the schemes are vulnerable to secret key breach. In this paper, we propose a secure and efficient covert communication scheme for blockchain-integrated SAGINs, dubbed CC-BSAGINs, to free the sender from maintaining secret keys. The key technique is to map the covertly sent data to some transactions on the underlying blockchain in a secure and efficient way; the mapping information is sent via a covert communication algorithm. Such a two-step mechanism releases the sender from key management and does not require the ciphertext to be communicated. We provide formal security proofs and conduct a comprehensive performance evaluation, which demonstrates the security and efficiency of CC-BSAGINs.