[572] in Kerberos
Re: password checking
daemon@TELECOM.MIT.EDU (Bill Sommerfeld)
Sun Jan 8 16:54:31 1989
From: Bill Sommerfeld <wesommer@ATHENA.MIT.EDU>
To: Jerome H. Saltzer <Saltzer@ATHENA.MIT.EDU>
Cc: Jeffrey I. Schiller <jis@ATHENA.MIT.EDU>, kit@ATHENA.MIT.EDU,
In-Reply-To: Jerome H. Saltzer's message of Sun, 8 Jan 89 01:00:51 EST,
I have a couple of arguments which are against central checking:
1) It would be nice to be able to allow a service to change its own
service key. Since there is no person involved who has to type the
password, there is no need for the key to be deriveable from a known
ASCII string... it should just be 56 randomly chosen bits (plus
parity). [This is really an argument for a way to end-run around the
quality checks.]
2) There was a proposal made that in a future version of Kerberos, the
string_to_key algorithm should be modified to include a per-realm
seed, so that if a user with an identity in more than one realm used
the same password string for several realms, compromise of one realm
would not lead to compromise of the user's identity in another realm.
This implies that the KDC should never see the un-hashed password at
all.
By the way, I'm not trying to argue that using the same password in
multiple realms is a good thing. I think that people will do it
anyway (and it's kind of hard to prevent), and seeding the
string_to_key algorithm with the realm name is a way to make that less
damaging.
- Bill
