If you’re using an ECC certificate with HTTP/2, you may get the following error from Google Chrome:
ERR_SPDY_INADEQUATE_TRANSPORT_SECURITY
If you googled about it you will finally find the following HTTP/2 requirements:
A deployment of HTTP/2 over TLS 1.2 SHOULD NOT use any of the cipher suites that are listed in the cipher suite black list (Appendix A).
and…
The black list includes the cipher suite that TLS 1.2 makes mandatory, which means that TLS 1.2 deployments could have non-intersecting sets of permitted cipher suites. To avoid this problem causing TLS handshake failures, deployments of HTTP/2 that use TLS 1.2 MUST support
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256[TLS-ECDHE] with the P-256 elliptic curve [FIPS186].
So you need the following cipher suite at the beginning of your suites:
ssl_ciphers ECDHE-RSA-AES128-GCM-SHA256
In my case if you’re using an ECC certificate you will need:
ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256
According to the specs:
Note that clients might advertise support of cipher suites that are on the black list in order to allow for connection to servers that do not support HTTP/2. This allows servers to select HTTP/1.1 with a cipher suite that is on the HTTP/2 black list. However, this can result in HTTP/2 being negotiated with a black-listed cipher suite if the application protocol and cipher suite are independently selected.
You can use black-listed cipher suites for backward compatibility.