pptpd+freeradius+ldap: which password encryption can I use?

Hi Everybody, I'm trying to setup a PPTPD server which would authenticate users using my openLDAP user database, in doing so I need freeradius. By now the only setup that actually works is: users in LDAP with clear text password. Obviously I want to use some kind of encryption for passwords and I don't like the solution of using cleartext passwords and the use of a specific user allowed to access to the password attribute, so my question is: which other possibilities I have? Looking to this table http://deployingradius.com/documents/protocols/compatibility.html I understand that I can use pap + sha1 but I can't understand how. Can anyone help me understand what is possible and what not? Many thanks Alberto