For this task, the more prudent design is to use a *different* set of
keys between the proxies and the real server (this key, C2, need only
be trusted by the proxies as the client never sees it).
This way, if the server is compromised through a security hole in the
more complex server software, the compromised private key is useless
outside the network behind the proxies and can be replaced as part of
routine restore of the server from backups, without affecting the
clients. The private key that clients trust (K1 matching C1) is known
only by the much simpler proxy servers, which contain much less code,
and thus a statistically smaller risk of being "hacked".
On 21-07-2010 21:08, PS wrote:
Well, think of the device as proxy which acts as the client to the server
and server to the client. Hence, the proxy is configured with the same
public-key and private key as that of the server so that it can act as the
server to the clients. But before it starts to do that, I want to make sure
that the server is using the exact same pub/pvt key pair as the one
configured on the proxy. Hence, the question.
So, given your response, I take it that if I compare the Pub-key in C2
(which came on the wire) with the Pub-key in C1, then I can indirectly infer
that the private-key corresponding to C1 and C2 is the same. In other words,
if the pub-key for 2 certs match, then they must have the same private-key.
On Tue, Jul 20, 2010 at 10:41 PM, Kyle Hamilton<aerow...@gmail.com> wrote:
Your question makes no sense.
If you know PK1 (contained in C1), and you know K1, then if you
receive C2 that contained PK1, you know that someone's trying to make
you think you're talking to yourself. (Nobody else can, by the rules
of PKI, have K1 but you -- which is why the challenge/response
protocol exists, to prove that you are who you say you are. If the
asserter of the identity contained in C2 can also prove that it knows
the private key K1 -- which it would have to if that other certificate
contained PK1 -- then you know you *are* talking to either yourself or
someone who somehow got your private key, which should be disturbing
if you aren't expecting it.)
But, if you simply want to know if it's possible to prove that two
public keys are identical by byte-comparison, you would either have to
extract the public key from the subjectPublicKey portion of the
certificate in the format that your own system would understand before
you could do that kind of byte comparison, or byte-compare the
DER-encoded keys from the certificates themselves.)
-Kyle H
On Tue, Jul 20, 2010 at 11:40 AM, PS<mytechl...@gmail.com> wrote:
Let us say I have a certificate and a private key pair (C1, K1)
Now, lets say I received a Certificate, C2 on the wire. Now, I want to
know
whether the pvt-key K1 corresponds to the private key of C2. One method
is
encrypt a Known random number with pub-key in C2 and decrypt with K1 and
see
if the number is same. But this is expensive.
I thought of another method and wanted to know if this is correct:
Do a byte-for-byte compare of the pub-key in C1 with that of C2. If they
are
same, then we can assume that K1 must be the private-key of C2. Am I
correct?
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