🚀 go-pugleaf

Craig Presson is correct that the cat is already out of the bag. It is
now common to use a variety of non-standard compression schemes to
upload and download files. (By non-standard, I mean non-CCITT.) They
include zip, arc, stuffit, compactor, etc.

The Feds cannot tell by inspection whether such schemes conceal
encrypted traffic. Moreover, the schemes themselves permit encryption
of the "plaintext" material in the uncompresses files in many cases.
At least one uses a scheme secure enough that it is non-exportable.

In order for them to tell whether such schemes conceal encrypted traffic,
they would have to intercept all such files and attempt to uncompress them.
Absent a probably cause warrant, it's hard to see how they'd get away
with this, at least under present law. Even in cases where they are
allowed to surveil traffic (such as the case of a link from the U.S.
to a foreign country), discovery that a message couldn't be uncompressed
into plaintext would do them no good unless they could establish
probable cause to seek the traffic formally. That is, they'd need
to reveal they'd monitored someone's messages, and then use the
encryption itself as "probable cause." It's hard to imagine
a warrant issuing from a sane judge for Joe Citizen in such cases,
thought one might against Mata Hari, recently emigrated to the U.S.
from Libya, and formerly known to be an employee of the Libyan
Intelligence Service.