"issuer" is somewhat of a misnomer from the OIDC breakdown of authentication / authorization parties. What we mean by "issuer" here is actually more like "notary" or "authorized verifier". However, since the "iss" field is already standardized, we keep that name for consistency.

What's to be implemented:

Looking at https://oauth3.org/.well-known/oauth3/directives.json, the core issuer components are these:

api:                    api.:hostname
create_jwk:             :scheme//:hostname/api/issuer@oauth3.org/jwks/:sub
jwks:                   :scheme//:hostname/api/issuer@oauth3.org/jwks/:thumbprint.json
grants:                 :scheme//:hostname/api/issuer@oauth3.org/grants/:sub/:azp?
credential_meta:        :scheme//:hostname/api/issuer@oauth3.org/logins/meta/:type/:id
credential_otp:         :scheme//:hostname/api/issuer@oauth3.org/otp
authorization_decision  :scheme//:hostname/api/issuer@oauth3.org/authorization_decision
authorization_dialog    :scheme//:hostname/api/issuer@oauth3.org/authorization_dialog
logout                  :scheme//:hostname/api/issuer@oauth3.org/#/logout

No access_token endpoint is strictly necessary. Since clients can create and manage their identity, the can sign create their own tokens. If the identity is stored on the issuer, then the issuer can also sign tokens. Doing so gives full control of all resources owned by the subject "sub" to the issuer "iss".

create_sub:       :scheme//:hostname/api/issuer@oauth3.org/subs/:secret/:sub

And here are some others that are useful, but could be implemented differently without breaking the protocol.

credential_create: :scheme//:hostname/api/issuer@oauth3.org/logins
credential_meta: :scheme//:hostname/api/issuer@oauth3.org/logins/meta/:type/:id
credential_otp: :scheme//:hostname/api/issuer@oauth3.org/otp

subject

The sub field must be sha256(secret + ':' + azp).

Example:

var secret = '8f7acd369764df342d1581872ff5f70fcc261aa116b3c41dee7ca3474ee2020f' // cryto.randomBytes(32).toString('hex')
var sha256 = cryto.createHash('sha256');
sha256.update(new Buffer(secret, 'hex'));
sha256.update(':' + 'example.com');

var sub = sha256.digest('hex');

This way any issuer can transfer ownership of identity to any other issuer and deterministically reproduce the ppid by virtue of the secret identity of the subject and the public identity of the authorized party and the key is known to be good if the issuer "iss" can supply the public key that verifies the token, identified by its thumbprint "kid" (which the issuer knows without revealing its ppid of the subject and without the authorized party needing to reveal its ppid of the subject.

jwks

The jwk endpoint needs to reveal the jwk by thumbprint as well as some