Right now, dkim-filter.8 and dkim-filter.conf.5 state, that the signing algorithm depends on openssl 0.9.8. However this is wrong, since e.g. even openssl 0.9.7 can be enhanced to use arbitrary mechanisms, digests, ciphers (BTW: not only in theory, I actually did that for solaris 10).
Instead the man pages should refer to 'dkim-filer -V' to see what algorithms are available and give a hint for the default.
suggested patches are attached.