This Small Business Innovation Research (SBIR) Phase I project develops a new biomolecular covert taggant method that marks objects with synthetic DNA nano-scale biosensors, called ComDTags, for verification of authenticity and for forensic track and trace-back. Pharmaceutical companies, brand owners and governments need thousands of covert and unique signatures to protect their drugs, products, documents and citizens. Using DNA for this purpose is environmentally safe, but to date, no DNA taggant method can produce enough unique and information-rich signatures. This project expects to demonstrate that the ComDTag DNA taggant system can easily construct millions of unique, information-rich and covert DNA signatures and that these signatures can be detected and decoded only by authorized users. The broader impacts of this research are anti-counterfeiting, authentication and quality control technologies. Counterfeiting costs the U.S. economy $200 billion per year and is responsible for the loss of 750,000 American jobs. The counterfeiting of the drug heparin has been linked to the deaths of over a hundred Americans with hundreds more having severe allergic reactions. These disturbing facts indicate that there is an increasing need for safe and covert methods to prevent, track and trace-back counterfeit products. Covert ComDTag signatures can feasibly meet these needs. Combined with more overt taggant products, ComDTag signatures can yield more robust, secure and useful covert track and trace-back solutions for commercial and national security interests.