I am in progress of trying to get maximum (or almost maximum) score on SSL Labs my site:

I currently don't understand why it does not give me full Key exchange score.

Now, it looks like this:

SSL Labs Key exchange < 100%

In spite of, I have generated 4096 DHParameters file, and tried many other things, like buying new certificate of 4096 size.

So, my question for you will be:

SSL Labs Key exchange is less than 100%, why? And how do I make it full?

OS: GNU/Linux Debian 9.2 with Apache 2.4.

  • 3
    You got an A+ but that isn't good enough? At some point you have to stop optimizing. Commented Nov 26, 2017 at 14:05

1 Answer 1


In the following file:


It was necessary to append these lines to ensure the highest grade of key exchange:

SSLOpenSSLConfCmd ECDHParameters Automatic

SSLOpenSSLConfCmd Curves secp521r1:secp384r1

UPDATE 2018-Apr-14

I found out, that (at least Chrome, read more on this topic here), decided to go for lower Key Exchange negotiation, namely P-256 (prime256v1 in Apache2, though SSL Labs reports it like secp256r1) in spite of me having set the above curves.

So, I guess we should add P-256 to the list; please change the second line to:

SSLOpenSSLConfCmd Curves secp521r1:secp384r1:prime256v1

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