1. An apparatus comprising: a memory operable to store a first risk token computed based on an initial set of attributes; and a processor communicatively coupled to the memory and operable to: receive a token indicating a change has occurred during a session, wherein: the session facilitates access to a resource; and the token indicates the first risk token should be recomputed to form a second risk token; determine, from the token, a first set of attributes, the first set of attributes comprising attributes required to compute the second risk token; determine that a cache contains a set of cached attributes; examine attributes in the set of cached attributes; determine at least one new attribute in the first set of attributes that is not in the set of cached attributes; retrieve the at least one new attribute; add the at least one new attribute to the cache, wherein the at least one new attributed is used in the generation of the second risk token; and determine and remove each of the attributes in the cache that are not in the first set of attributes such that the cache contains a second set of attributes that comprises only attributes in the first set of attributes.