problem with EAP-TTLS logging passwords

[Riccardo Veraldi]

Hello,
I use EAP-TTLS with PAP in my radius proxy infrastructure.
The problem is that with option

log_auth = yes
log_auth_badpass = yes
log_auth_goodpass = yes

passwords are logged on the intermediate radius servers and also on the 
final
hub radius server since I have a tree radius server infrastructure 
sparse into Italy.

How to solve this problem ?
I cannot use EAP-MD5 or MSCHAPv2 inside the TLS tunnel since users passwords
are on an encrypted database (unix passwords or kerberos passwords).

Anyone has a solution for this ?
I would like to prevent the possibility of the password being logged on 
the intermediate
radius servers.

thanks

Riccardo