Implementing OpenSSH-lpk for Active Directory 2003

Hi there,
We are trying to implement the open-ssh-lpk and we use Active Directory 2003 server as out LDAP server.
While trying to add the schema requested we are facing some problem with adding:

objectclass: posixAccount
objectclass: ldapPublicKey

It seems that it can't be done over Active Directory, look at the following link:

http://msdn2.microsoft.com/en-us/library/ms679016.aspx

Does someone has ever tried implementing it on Active Directory ?

Thanks,
Idan.

deshe.idan@...