According to one embodiment, an apparatus may store a plurality of tokens. The apparatus may receive a subject token indicating an attempt to authenticate a user. The apparatus may determine at least one token-based rule based at least in part upon a token in the plurality of tokens and the subject token. The at least one token-based rule may indicate a plurality of attributes required to access a resource. The apparatus may determine a second plurality of attributes represented by the plurality of tokens and the subject token. The apparatus may determine at least one missing attribute, which may be in the plurality of attributes but not in the second plurality of attributes. The apparatus may then request the at least one missing attribute, and in response, receive at least one token representing the at least one missing attribute.