Enhancing the security of electro-optic delayed chaotic system with intermittent time-delay modulation and digital chaos

•By using the optical switch technology, time-delay is not directly modulated.•The time delay is modulated in a hopping manner, continuous varying of the time delay is no longer needed.•From the communication point of view, the synchronization of the EO chaotic system for chaos communication will not be affected by the ITDM strategy.•From the security view point, time-delay signature can be successfully concealed in our scheme and the key space is also enlarged by adopting the digital chaos.

We propose a method whereby an intermittent time-delay modulation (ITDM) scheme and a digital chaotic system are introduced to enhance the security of electro-optic (EO) delayed chaotic system. An encoded digital chaotic sequence (EDCS) is used to switch the candidate time-delays. The detailed conditions for setting the proper ITDM strategy are studied by means of simulation. Under the certain conditions, the time-delays signature can be successfully eliminated. Meanwhile the dimension space of the secure parameters is increased by introducing the digital chaotic system.