putting binary data in a char field?

I'm attempting to use spamassassin 3.0 (beta) with an SQL backend, and have
identified one performance gain so far that makes PostgreSQL a good (IMO)
candidate for the backend. I need some advice though on another aspect--
instead of storing each token as text in the database, the token is being
sha1()'d and then possibly pack()'d.

That's all just background for my real question-- is there anything in the
standards (or elsewhere) that says you can't put binary(**) data into a char
field? When I changed the field to a bytea, processing time was
significantly reduced.

(**) Based on what very little I know of sha1 and of the tokens that have
been created by SA, it certainly looks like it's binary data that is being
inserted into the char field.

Thanks,
-ron