a method of validating a merchant in a point of sale transaction system , comprising the steps of encrypting a customer secret identification information using a public key of the merchant , entering the encrypted information into a transaction device , transmitting the encrypted information from the device to a merchant , decrypting at the merchant and the encrypted secret identification information , and transmitting the decrypted secret identification information from the merchant to the device wherein the customer verifies the decrypted secret identification information by visual inspection of the secret identification information .