authlogic - error messages

Hi my name is Marcos.
we've implemented authlogic in our project, but we need to replace the
errors messages.
for example:
* is too short (minimum is 6 characters) # when you don't introduce your
email for registration
* is too short (minimum is 4 characters) # when you don't introduce a
password
* should look like an email address. # when you introduce something that
it is not an email address
* doesn't match confirmation #when the pass and the confirmation doesn't
match

where do i have to set the new messages and how? is it at the model o
the controller?

tanxs!