how secure is secure apt?

["Michael Gilbert" <michael.s.gilbert@gmail.com>]

hello,

i just wanted to poll the debian community on whether they think that
using secure apt to upgrade/install packages over coffee shop wifi is
any more or less secure than doing the same via a home connection over
say roadrunner?

as i see it, there is an increased chance of a middleman (at the
coffee shop hop) masquerading as ftp.debian.org.

i guess this brings up a larger question: if there ever is a middleman
with the intent of getting malicious software onto my system, is it
possible for him to convince my secure apt that his packages are
legit?

thanks.

mike