A logic signing technique was developed to protect printed information from being forged, tampered with or possessed illegally. The technique was applied to anti-counterfeit authentication system of printed information to make it verified feasibly, quickly, conveniently and precisely. Its prototype was designed and implemented. The authentication system was totally independent of database and network. What’s more, it is open and secure cryptographically due to the fact that the synthetic information on a printed certificate is associated logically with encrypted verification information, which essentially changes the mode of the existing anti-counterfeit techniques for printed information.
