An authentication system to authorize access to data to be protected, including a token having a memory that stores: an array containing alphanumeric information and random data; and a seal scheme vector containing information to enable access to each of the information items in their respective positions in the array. The authentication system is configured to: subject access to the token to the insertion of a password; decrypt the seal scheme vector; acquire the arrangement information and the size information of each random data from the seal scheme vector; check correspondence between the acquired arrangement information and the effective arrangement of the information in the array, and between the acquired size information and the effective size of the random data; authorize or deny access to the data to be protected on the basis of a result of the previous check.