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.