Abstract: A simplified authentication system for communicating devices having fewer security requirements than conventional cryptographic systems. The device to be authenticated includes a secret, a function component for generating a random number, a function component for exchanging messages with other devices and finally an algorithm for calculating a hash using random number and secret. The device requesting authentication includes a secret and an algorithm for calculating a hash using a random number received from the device to be authenticated. A function component for comparing both hashes may be implemented in both devices. If the hashes calculated by both devices match it can be assumed that the authentication was successful. Preferably, this system and method may be used within a communication structure using portable communication devices like smartcards, personal digital assistants or mobile phones. Neither an exchange of the plain secret itself nor the storage of digital keys is required.