Re: Questions about secure curves
To clarify, Firefox/Mozilla the organization enforces an unexplained policy of prohibiting all included CAs from issuing any P-521 certificate, thus effectively banning their use on public servers regardless of technical abilities. On 15/10/2019 19:02, Mark Hack wrote: I believe that Firefox does still support P-521 but Chrome does not. Also be aware that if you set server side cipher selection and use default curves, that OpenSSL orders the curves weakest to strongest ( even with @STRENGTH) so you will end up forcing P-256. On Tue, 2019-10-15 at 17:24 +0200, Jakob Bohm via openssl-users wrote: 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 https://safecurves.cr.yp.to/. 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. safecurves.cr.yp.to lists some curves that Daniel J. Bernstein (who runs the cr.yp.to 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 promote. 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. Enjoy Jakob -- Jakob Bohm, CIO, Partner, WiseMo A/S. http://www.wisemo.com Transformervej 29, 2860 Soborg, Denmark. Direct +45 31 13 16 10 This public discussion message is non-binding and may contain errors. WiseMo - Remote Service Management for PCs, Phones and Embedded
Re: Questions about secure curves
On Oct 15, 2019, at 1:02 PM, Mark Hack wrote:I believe that Firefox does still support P-521 but Chrome does not. Also be aware that if you set server side cipher selection and usedefault curves, that OpenSSL orders the curves weakest to strongest (even with @STRENGTH) so you will end up forcing P-256.The choice is optimized for reasonable security, performance andinteroperability. There's little reason at present to prefer the521-bit or 384-bit NIST curves. If any of them are weak againsta secret new cryptanalytic attack, they possibly all are. Barringsecret advances at NSA (or similar), all the curves are well ouof reach of known realizable attacks (we don't have any scalablequantum computers at present), so you may as well use one withdecent performance.Similarly, IIRC Chrome prefers AES128 or AES256, ...-- Viktor.
Re: Questions about secure curves
I believe that Firefox does still support P-521 but Chrome does not. Also be aware that if you set server side cipher selection and use default curves, that OpenSSL orders the curves weakest to strongest ( even with @STRENGTH) so you will end up forcing P-256. On Tue, 2019-10-15 at 17:24 +0200, Jakob Bohm via openssl-users wrote: > 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 https://safecurves.cr.yp.to/. > > 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. > > > > safecurves.cr.yp.to lists some curves that Daniel J. Bernstein > (who runs the cr.yp.to 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 > promote. > > 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. > > > Enjoy > > Jakob
Re: Questions about secure curves
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 https://safecurves.cr.yp.to/. 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. safecurves.cr.yp.to lists some curves that Daniel J. Bernstein (who runs the cr.yp.to 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 promote. 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. Enjoy Jakob -- Jakob Bohm, CIO, Partner, WiseMo A/S. https://www.wisemo.com Transformervej 29, 2860 Søborg, Denmark. Direct +45 31 13 16 10 This public discussion message is non-binding and may contain errors. WiseMo - Remote Service Management for PCs, Phones and Embedded
Re: Questions about secure curves
On Tue, 2019-10-15 at 15:43 +0200, 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 https://safecurves.cr.yp.to/. > 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. > > Or what am I missing? They are not 'safe' in the sense the page above declares some elliptic curves to be safe. In particular these curves do not have some good properties the safe curves have. On the other hand that does not mean these curves are inherently insecure. -- Tomáš Mráz No matter how far down the wrong road you've gone, turn back. Turkish proverb [You'll know whether the road is wrong if you carefully listen to your conscience.]
Re: Questions about secure curves
There is nothing known to be wrong with NIST P256. If you don't have a known reason to use 384, then don't use it.
Questions about secure curves
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 https://safecurves.cr.yp.to/. 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. Or what am I missing? Shade and sweet water! Stephan -- |If your life was a horse, you'd have to shoot it.|
