A mobile wireless terminal, the terminal comprising a generator configured to generate and store a first numerical chain comprising a series of n values using a one-way coding function such that a given value within the chain is easily obtainable from a subsequent value, but the subsequent value is not easily obtainable from that given value, and an authentication requester configured to disclose a value from the numerical chain to an access node, in order to allow the access node to authenticate the mobile wireless terminal, wherein the disclosed value succeeds any values in the chain already disclosed by the mobile wireless terminal.