Anti-theft system and how to reset it without key?

Is the security light flashing? if so the alarm system is engaged, you can try a hard reboot which is done by removing the negative side of the battery, with the cable loose from the negative side of the battery, hold it to the positive terminal for 1 minute this will discharge the memory capacitors in the BCM and PCM allowing the system to reboot. If this doesn't work, I would call a mobile locksmith who can make a new code key for you which should cost about $280.00. Let me know what happens. This guide might help as well:

https://www.2carpros.com/articles/how-to-reset-a-security-system

Please go over this guide and report back.