Subject: Re: Kerberos: telnet to Solaris -> Bad encryption type
To: Johan Danielsson <>
From: Steven M. Bellovin <>
List: tech-security
Date: 09/27/2005 09:14:31
In message <>, Johan Danielsson writes:
>"Steven M. Bellovin" <> writes:
>> Why do you say this?  As far as I know, there are no generic attacks 
>> against CFB, and the weakness of DES is (and always has been) against 
>> brute-force key search, which 3DES defends against.
>Maybe I'm wrong. If the weakness of CFB lies only in the crypto used,
>then 3DES is a lot better. Also telnet doesn't implement any integrity
>by itself, and CFB doesn't help much either.

Lack of integrity-checking in a crypto protocol is indeed serious.  For 
telnet, it's' slightly worse for CFB than for CBC, but both are 
seriously flawed against replay attacks.

		--Steven M. Bellovin,