Personal security system

A method for verifying the identity of a system user comprising the steps of:

• providing an output from a token associated with the user which is a predetermined function of at least a portion of a stored seed, said providing step including the steps performed at said token of receiving a selected input code, processing said input code to generate a pseudo-random seed, storing the pseudo-random seed, generating a trigger signal at selected time intervals, operating in response to each trigger signal to utilize a value which is a predetermined first function of each stored seed as an input to said processing step, said processing step generating a new pseudo-random seed as a result thereof which is stored in place of the previously stored seed, the outputted function being a second function of at least a portion of each stored seed;
• and
• verifying the identity of the user at a verification unit, said verifying step including the steps performed at said verification unit of receiving a user identification and the token output, generating the second function of the seed which should be stored for the user with the token, and comparing the received outputted second function of the stored seed with the corresponding generated second function of the seed to verify the identity of the user.