On Sun, Sep 01, 2013, Viktor Dukhovni wrote: > > Incidentally, I just noticed the undocumented > SSL_CTX_set_tmp_ecdh_callback(), which has the same interface as > SSL_CTX_set_tmp_dh_callback(3) and it seems is also called with > keylength equal to either 512 or 1024. What is the meaning of > the keylength in this context? >
The keylength parameter and indeed is pretty useless (it was just copied from the DH version) the best it can be used for is to determine if the ciphersuite is export or not. > I have been using the equally undocumented SSL_CTX_set_tmp_ecdh(), > which just sets a fixed curve for all EECDH cipher-suites. Is there > any disadvantage to this approach? > Just setting P-256 should be fine for most circumstances just about everything supports it. The only thing it will cause problems with is SuiteB and 192 bit security mode but you really need (unreleased) OpenSSL 1.0.2 or later to handle SuiteB properly. For OpenSSL 1.0.2 the EC curve negotiation has been overhauled. Both client and server can set curve preferences and by calling: SSL_CTX_set_ecdh_auto(ctx, 1); the curve to use is handled automatically. Steve. -- Dr Stephen N. Henson. OpenSSL project core developer. Commercial tech support now available see: http://www.openssl.org ______________________________________________________________________ OpenSSL Project http://www.openssl.org User Support Mailing List openssl-users@openssl.org Automated List Manager majord...@openssl.org
