Traditional covert transmission (CT) approaches have been hindering CT application while blockchain technology offers new avenue. Current blockchain-based CT approaches require off-chain negotiation of critical information and often overlook the dynamic session keys updating, which increases the risk of message and key leakage. Additionally, in some approaches the covert transactions exhibit obvious characteristics that can be easily detected by third-parties. Moreover, most approaches do not address the issue of decreased reliability of message transmission in blockchain attack scenarios. Bitcoin- and Ethereum-based approaches also have the issue of transaction linkability, which can be tackled by Monero-based approaches because of the privacy protection mechanisms in Monero. However, Monero-based CT has the problem of sender repudiation. In this paper, we propose a novel Monero-Based CT approach (MBCT), which enables on-chain session key dynamically updating without off-chain negotiation. MBCT can assure non-repudiation of transmission participants, confidentiality of keys, reliability of message transmission and less observable characteristics. There are achieved by the three components in MBCT, namely, a sender authentication method, a dynamically on-chain session key updating method and a state feedback method. We implement MBCT in Monero-0.18.1.0 and the experiment results demonstrate its high embedding capacity of MBCT.

翻译：传统隐蔽传输方法限制了其应用，而区块链技术提供了新的途径。当前基于区块链的隐蔽传输方法需离线协商关键信息，且常忽略动态会话密钥更新，增加了消息泄露和密钥泄露的风险。此外，某些方法的隐蔽交易存在明显特征，易被第三方检测。多数方法未解决区块链攻击场景下消息传输可靠性下降的问题。基于比特币和以太坊的方法还存在交易可链接性问题，而门罗币的隐私保护机制可解决此问题，但基于门罗币的隐蔽传输存在发送方抵赖问题。本文提出一种新颖的基于门罗币的隐蔽传输方法（MBCT），实现无需离线协商的链上会话密钥动态更新。MBCT可确保传输参与方的不可抵赖性、密钥机密性、消息传输可靠性及低可观测性。这一效果通过三个组件实现：发送方认证方法、链上动态会话密钥更新方法及状态反馈方法。我们在Monero-0.18.1.0上实现了MBCT，实验结果表明其具有高嵌入容量。