"hide" values in a column

Background:  The maniacs I work for want an e-suggestion box.  The identity
of the suggestor must not be known, but the suggestion box administrator
must be able to respond privately back to that person so I can't just
completely leave out the identity of a suggestor against his/her suggestion.
The suggestor is meant to be have complete anonymity.

The real question:  How do I completely "hide"/encrypt the values in the
emp_id column even from me (who would be using psql) without the easy
possibility of decoding it?

CREATE TABLE suggestions (
emp_id INTEGER,
dtm TIMESTAMP,
comment TEXT,
private_response BOOL,
response TEXT,
);