17. The method of claim 15 , wherein, for a first archive file type of the plurality of different types of archive files, the descriptive information includes a hash value of the contained file in uncompressed format and a size of the contained file in uncompressed format.
19. The method of claim 17 , wherein, for a second archive file type of the plurality of different types of archive files, the descriptive information includes the hash value of the contained file in uncompressed format, the size of the contained file in uncompressed format, a size of the contained file in compressed format and a size of the contained file in compressed format.