The File Transfer Protocol does not offer any method to verify the
integrity of a transferred file, nor can two files be compared
against each other without actually transferring them first.
Cryptographic hashes are a possible solution to this problem. In the
past, several attempts have been made to add commands to obtain
checksums and hashes, however none have been formally specified,
leading to non-interoperability and confusion. To solve these
issues, this document specifies a new FTP command to be used by
clients to request cryptographic hashes of files.