An authentication token for authenticating more than one users or for securing interaction between said more than one users and one or more applications, the authentication token comprising: - a plurality of token instances, each token instance comprising instance data and each token instance associated with one of a plurality of at least two different users of the token whereby at least one different token instance is associated with each of said plurality of at least two different users, the authentication token being adapted to receive an additional token instance; the authentication token further being adapted to generate a dynamic credential using a secret credential generation key comprised in or derived from the instance data of a selected token instance of said plurality of token instances for authenticating a user associated with said selected token instance or for securing interaction between a user associated with said selected token instance and said one or more applications; whereby the authentication token is comprised in at least one of a plurality of token batches, whereby with each token batch of said plurality of token batches a value of a batch master key is associated and whereby the authentication token comprises the value of the batch master key of said at least one of said plurality of token batches that comprises the authentication token; the authentication token further being adapted to receive and process, as part of a first loading process stage for transferring to the authentication token a value of a user instance group master key, a first stage loading message that comprises a set of batch-related values, one batch-related value for each of said token batches, wherein the value of each batch-related value has been determined such that it is possible to calculate the same value of said user instance group master key, as a function of any pair of a batch master key of any particular one of said token batches and the batch-related value corresponding to that particular token batch, wherein said processing of said first stage loading message comprises: - retrieving from the first stage loading message that it has received a batch-related value that corresponds to the same token batch to which said batch master key, the value of which is comprised in the target authentication token, also corresponds; and - calculating the value of the user instance group master key as a function of said batch master key comprised in the target authentication token and said batch-related value that the target authentication token has retrieved from the first stage loading message; the authentication token further adapted to receive and process, as part of a second loading process stage for transferring to the authentication token a set of instance data values for the additional token instance, a second stage loading message that includes said set of instance data values for the additional token instance and that is secured with said user instance group master key or a key derived from the user instance group master key, wherein said processing of said second stage loading message comprises: - retrieving said set of instance data values from the second stage loading message it has received by using the value of the user instance group master key that the authentication token has calculated in the first loading process stage; and - determining the values of a set of secret keys of said additional token instance by using said retrieved set of instance data values, whereby said set of secret keys of the additional token instance comprises a secret credential generation key for the authentication token to subsequently use when generating dynamic credentials for said additional token instance. - a plurality of token instances, each token instance comprising instance data and each token instance associated with one of a plurality of at least two different users of the token whereby at least one different token instance is associated with each of said plurality of at least two different users, - retrieving from the first stage loading message that it has received a batch-related value that corresponds to the same token batch to which said batch master key, the value of which is comprised in the target authentication token, also corresponds; and - calculating the value of the user instance group master key as a function of said batch master key comprised in the target authentication token and said batch-related value that the target authentication token has retrieved from the first stage loading message; - retrieving said set of instance data values from the second stage loading message it has received by using the value of the user instance group master key that the authentication token has calculated in the first loading process stage; and - determining the values of a set of secret keys of said additional token instance by using said retrieved set of instance data values, whereby said set of secret keys of the additional token instance comprises a secret credential generation key for the authentication token to subsequently use when generating dynamic credentials for said additional token instance.