Delegation

Full Title or Meme

Delegation allows the owner of access to a resource to give some subset of that ability to another party.

Context

• The wiki page is focused on the need for a digital entity on the web to give some other party the ability to exercise some of the capability to some other digital entity.
• In the case of human users of the web they will have a User Agent through which they can express their intents on the web.
• Alternate terms are listed on the wiki page for Guardian.
• Some examples of delegation include:
  • A manager goes on vacation and provides a temporary replacement with the ability to control access to the division web site repository.
  • A person is declared unfit to manage their affairs by a court of competent jurisdiction and a guardian is appointed.
  • A parent and a child have the reversed case where the parent gives the child some ability to visit web sites that have age restrictions.
  • The president of the United States goes into surgery and passes control of the nuclear deterrent to the vice president.
  • A husband and wife grant each other authority to make medical decisions for the other with a defined set of limitations.
  • I add medical conditions to my smartphone so that any authorized EMT can view them if i am found comatose. (Here the delegation is to a situational role.)

Use Cases

• Delegate Credentials Use Case
• Delegated Authentication Use Case
• Delegated Authentication for User Managed Access
• Delegate to Trusted Assistant Use Case.

Actors

• A valuable Resource that is hosted on a Resource Server (RS). (Typically data, but it could also be a service API.)
• The Resource Owner (RO) that controls access to the Resource.
• The user of the Resource that receives the delegation token from the Resource Owner.
• The Relying Party (RP) that requests access to the Resource from the user.

Solutions

• For this wiki the solution will be some sort of digital token niblet that identifies the subject and is signed by the subject private key.
• The follows shows the elements of the niblet in json + jose({header}.{body}.{signature}) format that are included in the token.
• The best practice for this token is to send it as a signed, but not encrypted jose formatted string with a JWS signature. This will allow the token to be embedded in the grant that is sent to a relying party by the user; and then on to the resource server.

Element Name	Contents	Explanation for category	Cat
header	key info	required to validate the signature	MUST
sub	identifier of the RO	the grantor of access	MUST
puid	Persistent Identifier of RO	to handle recovery operation	MAY
user	Identifier of the recipient of this grant	Must be link to a signing key	MUST
Consent ID	Id of this consent	may be just a nonce, but intent is uniqueness	May
relation	of user to subject	array; parant; guardian; spouse; u13; minor; legal	MAY
aud	Identifier of the resource server	Must be link to a decryption key	MUST
scope	Identifier of the resource to be shared	array	MAY
stipulation	structure	limits the scope of the grant	MAY
exp	Unix epoch date	when delegation expires	MAY
trust_federation	a source of rules to evaluate	array eg HIPAA, GDPR	MAY
jwk	key of the sub (the signer)	include by value or by ref	MAY
authority	Id of the signer	only applies if guardianship.	MAY
signature	JWS	created by the sub's key (authority for guardianship)	MUST

• If a puid is used, there must be some mechanism to bind the puid to the sub that is outside the scope of this document. That mechanism will need to handle the recovery of access where the sub's authenticator cannot be used for any reason.
• Relationship is designed to show access rights of user over subject data. e.g. guardian of the person is a legal authority, u13 means the subject is a child under the age of 13, both of these gives the legal authority and so consent of the subject is not required. Minor means that the subject has not been emancipated but has some right over their own data. If the element is absent (or designated as "none"), the assumption must be that this is a pure delegation between consenting adults.
• Scope may be a purpose, for example, data is needed to fulfil the purposes of a prescribing physician. Such detailed scope are likely to depend on the trust_federation

References

• See also the wiki page on Consent Grant.