From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Curt Sampson <cjs(at)cynic(dot)net> |
Cc: | "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>, pgsql-hackers(at)postgresql(dot)org, pgsql-interfaces(at)postgresql(dot)org |
Subject: | Re: Speed of SSL connections; cost of renegotiation |
Date: | 2003-04-12 05:26:26 |
Message-ID: | 16304.1050125186@sss.pgh.pa.us |
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Lists: | pgsql-hackers pgsql-interfaces |
Curt Sampson <cjs(at)cynic(dot)net> writes:
> On Fri, 11 Apr 2003, Tom Lane wrote:
>> I realized this morning that there's probably a security tradeoff
>> involved: renegotiating the session key limits the amount of session
>> data encrypted with any one key, which is good; but each renegotiation
>> requires another use of the server key, increasing the odds that an
>> eavesdropper could break *that* (which'd let him into all sessions not
>> just the one).
> This seems extremely low-risk to me; there's very little data
> transferred using the server key.
Perhaps, but the downside if the server key is broken is much worse
than the loss if any one session key is broken. Also, I don't know
how stylized the key-renegotiation exchange is --- there might be
a substantial known-plaintext risk there.
The fact that sshd thinks it necessary to choose a new server key as
often as once an hour indicates to me that they consider the risks
nonnegligible.
regards, tom lane
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