Abstract: Different from traditional networks, there is often no contemporaneous end-to-end link between the source and destination in Delay/Disruption Tolerant Networks (DTN). So traditional security mechanism that based on central server is not suitable to DTN, and data dissemination in DTN faces the same challenge. This paper proposes an absolute distributed secure data dissemination mechanism for DTN. The mechanism adopts a distributed identity-based authenticated method, which is no need for a central Private Key Generator (PKG). Besides, depending on threshold cryptography and the mapping from category name to category key, the node only needs to communicate with random neighbor nodes whose number is no less than a certain threshold, and then it can acquire the data category key. Analytical and simulation results show this mechanism can guarantee the security requirements and greatly improve the efficiency of obtaining keys compared to method based on mobile key server, so it suits DTN very well.