A method for detecting counterfeit objects relies on participation by customers who check on the validity of the unique, random, and unpredictable ID assigned to each object. Potential counterfeiters cannot reliably guess valid IDs and also cannot easily acquire large numbers of existing valid IDs. Counterfeit pharmaceuticals are detected when customers report invalid IDs and when multiple customers report the same IDs or check their own past and present stock for duplicate IDs. Some counterfeits may be detected even when only a small percentage of customers participate. The method is well suited for single-dose ("unit of use") packaging, and can be adapted for resellers, wholesalers, repackagers, and other high-volume customers. The method can make pharmaceutical counterfeiting easier to detect and study, and make counterfeiting more difficult for the counterfeiters.
STATEMENT REGARDING FEDERAL RIGHTS
 This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy. The government has certain rights in the invention.