Questions about secure curves

Jakob Bohm jb-openssl at
Tue Oct 15 15:24:12 UTC 2019

On 15/10/2019 15:43, Stephan Seitz wrote:
> Hi!
> I was looking at the output of „openssl ecparam -list_curves” and 
> trying to choose a curve for the web server together with letsencrypt.
> It seems, letsencrypt supports prime256v1, secp256r1, and secp384r1.
> Then I found the site
> I have problems mapping the openssl curves with the curve names from 
> the web site, but I have the feeling that none of the choices above 
> are safe.
> lists some curves that Daniel J. Bernstein
(who runs the domain) wants to promote, and emphasizes
problems with many other popular curves.

prime256v1 = secp256r1 = P-256 and secp384r1 = P-384 are two curves
that the US government (NIST in cooperation with NSA) wants to

It so happens that the CA/Browser forum has mysteriously decided
that the big (US made) web browsers should only trust CAs that
only accept curves that the US government promotes.  So if you
want your SSL/TLS implementation to work with widely distributed
US Browsers (Chrome, Safari, Firefox, IE, Edge etc.) you have to
use the US government curves P-256 and P-384 .  The third US
governmentcurve P-521 is banned by Firefox, so no trusted CA can
support it.


Jakob Bohm, CIO, Partner, WiseMo A/S.
Transformervej 29, 2860 Søborg, Denmark.  Direct +45 31 13 16 10
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