Method of verifying authenticity of goods uses combination codes that have a random portion and a non-random portion that includes at least a secret portion that is encrypted. The combination codes are encrypted and may be applied to goods and checked to determine authenticity of goods; the secret portion may be encrypted with a public key and can be decrypted, for example, using a corresponding private key. The authenticity may include whether or not a tax or duty has been paid. The checking may include checking, e.g., viewing the non-random portion of the decrypted combination code to determine whether it is the same as the non-random portion used to compose the combination code.