Subject: server public key fingerprint?

From: "denis bider" <[email-masked]>
Date: Mon, 29 Jan 2001 04:27:52 +0100

Hello everyone,

is there a standardized fingerprint calculation method for verifying the
integrity of a server's public key? I searched the archives for the string
'finger', and it only occurs once - in a PGP-related header field of a
single message...

I would think a standardized fingerprinting method would be necessary in
order to facilitate interoperation of clients and servers from different
vendors. How can you call up a server's administrator to verify the public
key if your client calculates the fingerprint in a manner that is
incompatible with the server?

Regards,

denis

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From: [email-masked] (Niels M�ller)
Date: 29 Jan 2001 15:02:36 +0100

> 'finger', and it only occurs once - in a PGP-related header field of a

LSH currently uses the SHA1 hash of the canonical SPKI encoding of the
public key. I believe that OpenSSH calculates the fingerprint as the
SHA1 hash of the keyblob. And then PGP uses yet another different
fingerprinting method.

Some coordination would be desirable.

/Niels

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From: "denis bider" <[email-masked]>
Date: Mon, 29 Jan 2001 23:47:34 +0100

> > is there a standardized fingerprint calculation method for
> > verifying the integrity of a server's public key? I searched
> > the archives for the string 'finger', and it only occurs once
> > - in a PGP-related header field of a
> > single message...
>

Thanks to Niels for the above reply.

In the absence of any other comments, I would like to reiterate that this
issue seems crucial to me. I see no way to verify a public key fingerprint
unless the client and the server both support the same fingerprinting
method. Currently, this only seems to be the case when both the client and
the server are from the same vendor. But if the assumption of this standard
is that all clients will communicate with servers of the same vendor, why
bother with standardization of the SSH protocol in the first place?

Clearly, the assumption should be that clients from various vendors will
communicate with servers from various other vendors. Since verifying the
fingerprint of a server's public key is a key element of establishing a
secure connection, I think a method should be recommended, or even mandated,
by the SSH standard.

So, my suggestion would be that someone [who has more experience with SSH
than I do] drafts a paragraph to this effect and inserts it in a visible
spot of the SSH specification. Perhaps such a recommendation could be added
to the "SECSH Public Key File Format" document...?

Regards,

denis