[openssl-users] regarding SSL security

Karl Denninger karl at denninger.net
Fri Feb 12 20:15:23 UTC 2016

On 2/12/2016 11:37, R-D intern wrote:
> Thank you a lot, Jakob.I understood your answers and am quite satisfied too
> that the replies sound conceptually right. But it would be kind on your part
> if you answer some questions further.
> 1. Regarding question 3, I am using openssl 1.0.2e which supports named
> curve. Such a question had earlier been asked in this forum which says ,
> such a message is only misleading but the certificate works fine. Here is
> the below
> link:"http://openssl.6102.n7.nabble.com/ECC-Self-Signed-Certificate-td17042.html#a17047".But
> I would like the certificate have a clean structure. How can that be done?
> 2.Regarding question 7, I am working to secure a middleware that will be
> deployed in control and monitoring systems, hence there would be know
> persons at the client side and  the certificates I am  using are self signed
> ones created using openssl 1.0.2e , hence there will be no public CAs . In
> such a scenario , how will the CA know that the private  key has been
> compromised? If the private key  gets compromised, then even the certificate
> can be forged ,then what is the use of CRL?
>  Kindly answer. 
> Thanks and regards,
> Suman Patro

If the CA is private then the CA's public certificate (and any
intermediates required to reach it) is loaded into OpenSSL as the chain
of validation.  That certificate can specify an OCSP or CRL location for
revocation checks, which you must then extract and check in your code.

"Best practice" for something of this sort requires that _*both*_ ends
of the connection present and use certificates, not just the server (in
other words you don't want a random client machine connecting either!)
which in turn means you need to check for validity and revocation on
both ends, /*and */you must ensure the security of the CA infrastructure
and its private key.

Note that "how the CA knows the client private key is compromised" is an
/operational /question, not a programmatic one -- as is the case with a
public CA.  (In other words someone has to tell the CA it was stolen so
the CA can issue the revocation, and the application must check that
revocation resource.)

Karl Denninger
karl at denninger.net <mailto:karl at denninger.net>
/The Market Ticker/
/[S/MIME encrypted email preferred]/
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