1. A method comprising: receiving a first copy of a content dataset at a proxy server of a communications network without a corresponding request for the content dataset from a first client terminal over the communications network; calculating an anticipatory dataset as a function of the content dataset, such that the anticipatory dataset represents at least a portion of the content dataset but cannot be used to reconstruct the content dataset without a keying dataset that is also calculated from the content dataset; communicating the anticipatory dataset to the first client terminal from the proxy server over the communications network for anticipatory storage of the anticipatory dataset local to the first client terminal; and subsequent to communicating the anticipatory dataset to the first client terminal: intercepting a second copy of the content dataset at the proxy server, the second copy of the content dataset being communicated to the first client terminal in response to a content request issued by the first client terminal for the content dataset; calculating the keying dataset as a function of the second copy of the content dataset at the proxy server; and communicating the keying dataset from the proxy server to the client terminal for use by the first client terminal in locally reconstructing the content dataset as a function of the keying dataset and the anticipatory dataset; wherein calculating the keying dataset comprises extracting a hold-back portion of the content dataset to use as the keying dataset; and wherein calculating the anticipatory dataset as a function of the content dataset comprises removing the hold-back portion of the content dataset to generate the anticipatory dataset, so that the anticipatory dataset cannot be used to reconstruct the content dataset without the keying dataset.