A second data source may retrieve metadata for one or more versions of a set of versions of a file stored at the first data source. In some examples, the metadata for the one or more versions of the file may include at least an identifier of the file, a timestamp, and a cryptographic signature. In some examples, generation of the cryptographic signature may be based on the identifier of the file, the timestamp, and a cryptographic key. The second data source may identify a set of versions of the file that were uploaded from a trusted data source to the first data source based on a comparison of the cryptographic signature to a computed cryptographic signature. The second data source may then determine a targeted version of the file and retrieve the targeted version of the file from the first data source.