Re: ssl-enum-ciphers question

Robin,

One of the ciphers supported uses an Elliptic Curve Cryptography (ECC) key
exchange. In this case, ssl-enum-ciphers offers all published ECC curves
and lets the server pick one. The server picked the "secp256r1" curve,
which is a 256-bit curve having an equivalent strength to 3072-bit RSA. The
server's certificate has a key strength that is greater than 3072-bit RSA.
This could be 4096-bit RSA or 384-bit ECC. The intent of the warning is to
identify servers that are configured to negotiate a weaker connection than
the certificate is capable of.

This reminds me that we do not currently have a way of enumerating all the
ECC curves that a server supports. This would be an interesting data set
and could also show a weakness in cipher strength, since named curves go
all the way down to 1024-bit equivalent strength, and custom curves can be
512-bit or weaker.

Dan

On Wed, Apr 5, 2017 at 4:55 PM, Robin Wood <[email protected]> wrote:

> Hi
> Can anyone explain what this output from the ssl-enum-ciphers script means?
>
> |       Key exchange (secp256r1) of lower strength than certificate key
>
> Thanks
>
> Robin
>
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