Wireless communication is particularly vulnerable to signal jamming attacks. Spread spectrum mitigates such problem by spreading normal narrowband signals over a much wider band of frequencies and forcing jammers who do not know such spread pattern to invest much more effort to launch attacks. However, in broadcast systems, jammers can easily find out the spread pattern by compromising some receivers. Several group-based approaches have been proposed to deal with insider jammers who can compromise receivers in broadcast systems, they can tolerate t malicious receivers as long as the system can afford 2t additional copies for each broadcast message. This paper introduces a novel jamming-resistant broadcast system that organizes receivers into multiple channel-sharing broadcast groups and isolates malicious receivers using adaptive re-grouping. By letting receivers in different groups partially share their channels, this scheme reduces the extra communication cost from 2t to (2 − ρ)t copies, where ρ is the channel sharing factor (0