Openssh hash request

Theo de Raadt deraadt at cvs.openbsd.org
Sat Oct 15 16:15:51 EST 2005


> Please forgive if this is the wrong place...
> 
> As a user of the excellent ssh and sshd I would like to see the next
> version of openssh contain support for the SHA-2 hashes (SHA-256,
> SHA-384, and SHA-512) as the SHA-1 hash is now known to be vulnerable to
> a 2^69 and possibly a 2^63 key-space search.  As of version 0.98 openssl
> contained support for these hashes so it would be nice if openssh
> followed suit.
> 
> I posted this request before on comp.security.ssh and was correctly told
> that by default sshd regenerates the key every 60 mins.  But consider a
> server using SHA-1, and an attacker who wants the user/password, or a
> file being transfered, and captures the cipher data.  While they cannot
> see your session in "real time" they still could capture the data and
> key-search the SHA-1 hash, making it easier to break the key.
> 
> While I'm no crypto-expert, this does _NOT_ seem like a good thing(tm).
>  Are there any plans to implement these hashes into openssh?

Youare no crypto-expert, but as the SSH protocol uses these things
as HMAC varients, none of the above makes any sense.




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