The DVB-S (Digital Video Broadcasting - Satellite) was originally developed as a TV broadcasting protocol. Later on two encapsulation protocols were developed in order to allow network level TCP/IP encapsulation: Multi Protocol Encapsulation - MPE and Unidirectional Lightweight Encapsulation - ULE. This provided a high quality internet access via satellite, which can be multiplexed even with radio and TV transmissions. In this paper, we propose a security system for the ULE based on chaotic sequences for the key management and data encryption. The key management system is based on a multilayer key model. The proposed system provides security services responding to the security requirements of IP over satellite DVB. To quantify the efficiency of the proposed system, we have done a comparative study (theoretically and by simulation) of the data overhead for different transport protocols and different sets of security parameters. Obtained results confirm the efficiency of the proposed system.