OpenSSH and CBC

[Christian Weisgerber]

On 2015-06-15, Gerhard Wiesinger <lists at wiesinger.com> wrote:

> I saw that OpenSSH release 6.7 removed all CBC ciphers by default. Is 
> CBC therefore considered as broken and unsecure (in general or SSH 
> implementation)?

CBC modes in SSH use the last encrypted block of the previous packet
as the IV for the next packet.  The protocol is specified this way.

> I also read a lot of references (see below) but still not clear to me 
> what's the actual "security status" of CBC and why it has been removed 
> in general.

These are pertinent:

> http://www.kb.cert.org/vuls/id/958563
http://www.openssh.com/txt/cbc.adv

-- 
Christian "naddy" Weisgerber                          naddy at mips.inka.de