Pak transfers multiple, possibly very big, regular files between possibly different hosts you have shell access to. It transmits segment IDs instead of file names and uses on-the-fly Blowfish-CBC encryption while being absolutely restartable with practically no loss of data already transmitted. Encrypted pak streams can be stored in intermediary regular files on untrusted hosts. Several stored pak streams, even truncated ones, can be merged for re-piping without decryption. Integrity is never checked. File offsets of any magnitude are supported via recompilation (the default width is 64 bits). Either UNIX 95 or UNIX 98 conformance is required and sufficient.