Subject: Re: PROPOSAL: adding capability for blowfish passwords
To: Michael Eriksson <>
From: Steven M. Bellovin <>
List: current-users
Date: 06/06/2002 18:34:17
In message <>, Michael E
riksson writes:
>Steven M. Bellovin wrote:
>> In message <>, Tero Kivinen wr
>> >Actually I think the num_iterations should be stored along with the
>> >salt to the encrypted password. This way the num_iterations can be
>> >changed by changing the passwd.conf, and all new passwords would start
>> >using the new num_iterations. Also the default could be something
>> >like:
>> >
>> >num_iterations = time(NULL) / div + base;
>> >
>> >so it goes up over time, as the cpu speeds go up too... Of course the
>> >div and base could be parameterized in the /etc/passwd.conf too...
>> Clearly, the number of iterations for a given password must be stored 
>> with the hashed password.  My comment was about the number to be used 
>> at password change time.  Your default is interesting -- I was about to 
>> object that time() returns the number of seconds since the epoch, 
>> rather than a measure of the machine's speed -- until I realized that 
>> that was exactly what you meant!  Very clever...
>You are forgetting that Moore's law is exponential, not linear...

		--Steve Bellovin, (me) ("Firewalls" book)