Re: Telnet Encryption Specification

[Jeffrey Altman <jaltman at watsun.cc.columbia.edu>]

> "Theodore Y. Ts'o" <tytso at MIT.EDU> writes:
> 
> >> The fix for this would be to use CBC(*), but that has the down side of
> >> being slower and requiring more bytes on the wire, since telnet is a
> >> character-at-a-time protocol, and CBC requiers that you block data into
> >> 8 byte chunks.  (The advantage of CFB and OFB is that they work well
> >> with streaming protocols.)
> 
> Just as a point of reference, I regularly use ssh (which has quite a
> bit of overhead) for interactive traffic over a modem, and I can't
> detect any difference in latency over a non-protected connection.  I
> think the days where we need to worry about the extra overhead are
> also over.
> 
> 		Marc
> 

However, file transfers over a Kerberos Telnet connection from a 
166 MHz Pentium to a rather fast Sparc system run at about 60% of the
speed of an unencrypted connection.  This is due entirely to the
overhead of the encryption.  So I don't think the cost are completely 
irrelevant.


    Jeffrey Altman * Sr.Software Designer * Kermit-95 for Win32 and OS/2
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