A method of responding to a request for a key of a first length is provided. According to the method, the request for the key of the first length is received. Moreover, it is determined whether any one of a plurality of cached keys satisfies the request. If any one of the plurality of cached keys satisfies the request, a cached key of the first length is selected. Also, the selected cached key is removed from the plurality of cached keys. Thus, in response to the request, the selected cached key of the first length is provided.