Re: How to increase the priority of some cipher ?

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Obviously, the DH Ephemeral ciphersuites consist of a (sometimes
fast) DH step PLUS an RSA or ECDSA step to confirm the identity of
the server, while the slightly less secure RSA suites only do the
RSA step.  DH+ECDSA requires an ECDSA certificate, which won't
work for clients that require RSA suites.

On 26/09/2017 18:58, Benjamin Kaduk via openssl-users wrote:
I am curious about this statement that "(EC)DHE cost much more resources than RSA".  In particular, ECDHE is supposed to be less computation-intensive than RSA for a given security level, so it would be interesting to hear what your setup is where the reverse is supposed to be observed.

-Ben

On 09/26/2017 03:44 AM, 李明 wrote:
just find it,
 server respect client's cipher preference  by default,
 it selects the suite preferred by client among the cipherlist that both the client and server support.  so it's not enough to just increase RSA cipher priority on server side , SSL_OP_CIPHER_SERVER_PREFERENCE will make the server select the suite that itself most prefer among the cipherlist that both the client and server support.


在 2017-09-26 15:15:10,"李明" <mid_li@xxxxxxx> 写道:

    Hello,
       Currently, openssl prefer (EC)DHE handshakes over plain RSA,
    but (EC)DHE cost much more resouces than RSA.
       In order to get higher performance , I want to prioritize
    RSA related ciphers, does anyone knows how to do it.
       I have tried cipherlist "RSA:ALL:!COMPLEMENTOFDEFAULT:!eNULL"
    , it looks fine in openssl command line
    ./openssl ciphers -v 'RSA:ALL:!COMPLEMENTOFDEFAULT:!eNULL'
    AES256-GCM-SHA384      TLSv1.2 Kx=RSA      Au=RSA 
    Enc=AESGCM(256) Mac=AEAD
    AES128-GCM-SHA256      TLSv1.2 Kx=RSA      Au=RSA 
    Enc=AESGCM(128) Mac=AEAD
    AES256-SHA256          TLSv1.2 Kx=RSA      Au=RSA  Enc=AES(256)
    Mac=SHA256
    AES128-SHA256          TLSv1.2 Kx=RSA      Au=RSA  Enc=AES(128)
    Mac=SHA256
    AES256-SHA             SSLv3 Kx=RSA      Au=RSA  Enc=AES(256)
    Mac=SHA1
    AES128-SHA             SSLv3 Kx=RSA      Au=RSA  Enc=AES(128)
    Mac=SHA1
    ECDHE-ECDSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH     Au=ECDSA
    Enc=AESGCM(256) Mac=AEAD

     but, after SSL_CTX_set_cipher_list(ctx,
    "RSA:ALL:!COMPLEMENTOFDEFAULT:!eNULL")  in my application, it
    didn't work, the first choice is still ECDHE-RSA-AES256-GCM-SHA384

Enjoy

Jakob
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