1. A verification system for a computer software installation, comprising: a primary library file, the primary library file having a digital signature; a loader program arranged to obtain a digital signature key and further arranged to load the primary library file; and a plurality of secondary files arranged to be referenced by the primary library file, each of the plurality of secondary files having a digital signature; wherein the loader program is arranged to verify and selectively load the primary library file by comparing the obtained digital signature key with the digital signature of the primary library file, the primary library file being further arranged to subsequently verify and selectively load the plurality of secondary files by calling the loader program to compare the obtained digital signature key with the digital signature of each of the plurality of secondary files.