[openssl-users] Creating an X25519-based Certificate

[Michael Scott]

Thanks Erwann, but that's not an answer to my question.

To get the CA to sign (using RSA or anything) a certificate that contains
an X25519 public key, that certificate must first submit to the CA
something called a "Certificate request". This takes the form of the
supplicant certificate, which is self-signed. However you cannot self-sign
with an X25519 key (using the openssl command line tool), as it objects
that X25519 does not support signature.

So the issue arises around the "certificate request" process. There is I
agree no problem in creating the certificate itself.


Mike



On Wed, Jun 29, 2016 at 4:27 PM, Erwann Abalea <Erwann.Abalea at docusign.com>
wrote:

> Bonjour,
>
> You may have a classic certificate containing your
> {X,Ed}{25519,448,whatever} public key once:
>
>    - an OID is allocated to identify this type of public key (it will go
>    into tbs.subjectPublicKeyInfo.algorithm.algorithm)
>    - a set of associated optional parameters are defined for this OID (to
>    go into tbs.subjectPublicKeyInfo.algorithm.parameters)
>    - a canonical encoding for this type of public key is defined, so the
>    key material can be enclosed into tbs.subjectPublicKeyInfo.subjectPublicKey
>
>
> This certificate may be RSA-signed or ECDSA-signed (or whatever-signed, in
> fact).
>
> For a CA to be able to Ed{25519,448,whatever}-sign something, the previous
> steps must have been done, plus:
>
>    - an OID is allocated to identify the signature algorithm to apply (it
>    will not be ECDSA) -> cert.signatureAlgorithm.algorithm
>    - a set of associated optional parameters are defined for this OID ->
>    cert.signatureAlgorithm.parameters
>    - a canonical encoding for the signature value is defined, so it can
>    be enclosed into cert.signatureValue
>
>
> All this is being discussed at CFRG.
>
> Cordialement,
> Erwann Abalea
>
> Le 29 juin 2016 à 16:46, Michael Scott <mike.scott at miracl.com> a écrit :
>
> Hello,
>
>
> How do I do this? Using the OpenSSL command line tool, a certificate
> request must be self-signed, but the X25519 elliptic curve (newly supported
> in version 1.1.0), doesn't do signature, it can only be used for key
> exchange.
>
> (Of course the X25519 Montgomery curve is birationally equivalent to an
> Edwards curve which can do signature. And indeed it is our intention to use
> the Edwards curve. But first I need a CA-signed X25519 cert. But because of
> the above catch-22 problem, I cannot create one.)
>
>
> Mike
>
>
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