Indirect Identity Control: delegation, guardianship, and controllership – Daniel Hardman

Indirect Identity Control
delegation, guardianship, and controllership
Daniel Hardman, July 2019
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Sources
● These slides: http://bit.ly/2YczZzP
● Indirect Identity Control RFC: http://bit.ly/aries-rfc-103
● Appendix C of Sovrin Glossary: http://bit.ly/svrnglos-appC
● Sovrin Guardianship Task Force: http://bit.ly/svrn-guard-tf
ssimeetup.org · CC BY-SA 4.0 International

See Appendix C of the Sovrin Glossary.
Guardianship, delegation,
controllership
See Appendix C of the Sovrin Glossary: http://bit.ly/svrnglos-appC

Delegation
A corporation is governed by a
Board of Directors, executives,
and employees with multiple
levels of delegated authority.
The control relationships are
dynamic and complex.

Guardianship
Parents typically manage the
identities of their young children.
Adult children may need to exercise
the identity of a parent with
dementia, or of a parent who
recently passed away.

Controllership
A self-driving car may be capable
of many independent actions, but
behind such a smart device must
be a human entity that takes legal
responsibility. A pet needs a
proxy because it can’t be
self-sovereign.

◦ Mya (orphan girl in refugee camp)
◦ Patrick (father with family after hurricane destroys home; no
digital access)
◦ Tom (homeless, mentally ill, drug addict)
◦ Gayle (elderly, has moderate autonomy, needs digital
assistance)
◦ Soﬁa (trail runner disappears in the mountains)
◦ Rover (pet dog)
◦ Unproﬁtable, Inc (company in receivership)
◦ Hertz and Dave (rents car, gets delegated authority)
See “Persona and User Stories” at http://bit.ly/2GnRtTq
Formal Work on Use Cases

Guardianship: internal risk is pivotal
In SSI, risk mostly comes from external attacks.
But guardianship isn’t self-sovereign, by deﬁnition.
Guardians are an internal risk to dependents who
can’t manage keys or advocate/defend.
Pure crypto and cybersecurity don’t prevent
abuse. Protections must come from elsewhere.

Moments of risk
◦ When a transition happens
◦ Should it be happening now?
◦ Are the right people giving and getting the baton?
◦ Are the conditions, limits, and safeguards understood, evaluated, and
honored?
◦ When a constraint needs to be enforced
◦ Is there a limit on the time, place, or circumstances of guardianship?
◦ When stakes are high
Risk exists constantly; these are just hot spots. Small, incremental
actions away from these hot spots can change the evaluation at key
moments.

Who appoints a guardian
1. Dependent (“while I’m unconscious during surgery, Alice is my guardian”)
2. Legal authority (Court makes adult child a guardian for their parent with Alzheimers)
3. Self (girl wanders from jungle into refugee camp; lacking options, camp appoints itself)
4. Circumstances (parent or pet owner; implicit)
These methods do not carry equal trust, and they are not equally formal.

Evaluating conﬂicting guardianship assertions
Deciding who is the “proper” guardian requires human judgment.
The process may use credentials, but that’s not all it will use.
NGO: “I’m the guardian of Mya. Here’s my self-attested guardian cred.”
Fim (dad?): “No, I’m the guardian of Mya. Here’s Mya’s birth cert with my name on it.”
Ana (mom?): “No, I’m the guardian of Mya. Here’s Mya’s ration card with her photo.”
Court: “No, Ana is the guardian of Mya. Fim’s parental rights were terminated.”
Sometimes the proper guardian isn’t available, so we choose the
best available alternative.

Limits on guardians
1. Time (for what period(s) guardian has that status)
2. Place (in what physical or virtual locations guardian is valid)
3. Function (legal vs. medical vs. educational)
4. Circumstances (for particular event(s))
5. Biometrics (for dependent involvement)
6. Relationships (who guardian can connect to)
7. Attributes (data/credentials -- what guardian can prove)
8. Agents (what software/devices guardian can use)
9. Cooperation (with joint approval)
10. Oversight (audit trail, reporting)

“All of these forms of identity control share the
issue of indirectness. All of them introduce risks
beyond the ones that dominate in direct identity
management. All of them complicate information
ﬂows and behavior. And they are inter-related;
guardians and controllers often need to delegate,
delegates may become controllers, and so forth.
The solutions for each ought to have much in
common, too

A proxy trust framework that specifies the rules and
conventions in force for a particular class of indirect
identity control use cases.
A proxy credential that binds a controlled entity to its
proxy and clarifies the nature and limits of the control for
that specific relationship.
A proxy challenge that evaluates the proxy credential in a
particular context, proving or disproving the legitimacy of
indirect control and creating opportunities for auditing and
enforcement.
Common Solution Elements

Questions a trust framework answers
◦ What is its formal name and version?
◦ In what geos and legal jurisdictions is it valid?
◦ What are required or recommended behaviors, and how are they enforced?
◦ On what bases are proxies appointed? kinship, court_order, self_assigned...
◦ What are possible permissions of a proxy? ﬁnancial, medical, travel, relationships, admin...
◦ What are possible constraints on a proxy’s scope? geo_radius, jurisdiction, biometric_freshness...
◦ What auditing mechanisms are required or supported?
◦ What appeal mechanisms are required or supported?
◦ What proxy challenge procedures are best practice?
◦ What freshness rules are used for ofﬂine mode?
⇨ Example at
http://bit.ly/2YsZ7b7

“
Answers to name: Mya
Dependent
Gender: Female
Birthdate: 2014-01-01
Identifying marks: birthmark left shoulder, long scar above
left wrist
Answers to name: Zo
Guardian 1
Gender: Female
Birthdate: 1953-01-01
Identifying marks: arthritis, misshapen knuckles, both hands
Preparing
to issue a
proxy
credential

“
…(metadata not shown)…
trustFramework
auditURI
appealURI
credentialSubject
holder
basisURI
role
name
birthDate
gender
identifyingMarks
photo
constraints
boundaries
circumstances
proxied
permissions
photo
name
birthDate
gender
identifyingMarks
http://unicef.org/tf/camptf/1.0
http://myanmar.gov/oversight
http://myanmar.gov/arbitration
http://unicef.org/tf/camptf/1.0/self
camp
UNICEF
<blank>
<blank>
<blank>
<blank>
“Lotus” camp
until resettled
Mya
2014-01-01
F
birthmark left shoulder, long scar above left wrist
{“grant”: [“medical”, “school”, “food”],
“when”: {“roles”: “kin”}},
{“grant”: [“school”, “food”, “delegate”],
“when”: {“roles”: “camp”}},
{“grant”: [“unenroll”, “travel”],
“when”: {"n”: 2, “roles”: [“kin”, camp”]}}
UNICEF’s
credential

“ {“let”: “kin”, “do”: [
“medical”, “school”, “food”]},
{“let”: “camp”, “do”: [
“school”, “food”, “delegate”]},
{“let”: {"n”: 2, “of”: [“kin”, “camp”]}, “do”: [
“unenroll”, “travel”]}
…(metadata not shown)…
trustFramework
auditURI
appealURI
credentialSubject
holder
basisURI
role
name
birthDate
gender
identifyingMarks
photo
constraints
boundaries
circumstances
proxied
permissions
photo
name
birthDate
gender
identifyingMarks
http://unicef.org/tf/camptf/1.0
http://myanmar.gov/oversight
http://myanmar.gov/arbitration
http://unicef.org/tf/camptf/1.0/grandparent
kin
Zo
1953-01-01
F
arthritis, misshapen knuckles, both hands
<blank>
<blank>
(same as UNICEF’s)
Mya
2014-01-01
F
birthmark left shoulder, long scar above left wrist
Grandma’s
credential

Answers to name: Mya
Dependent
Gender: Female
Age: about 6
Looks like this?
Answers to name: Zo
Guardian
Gender: Female
✔
✔
✔
✔
Show more ways to check...
✔
✔
✔ Looks like this?
✔ Has ‘food’ permission for dependent
✔ No constraints
Proxy
Challenge
(food tent)

Answers to name: Ri
Dependent
Gender: Female
Age: about 6
Looks like this?
Answers to name: Kapa
Guardian
Gender: Female
✔
✔
✔
✔
✔
✔
✔ Looks like this?
✘ Has ‘travel’ permission for dependent when acting jointly
with another guardian with role “camp”: Add guardian...
Proxy
Challenge
(travel)

Questions?
● These slides: http://bit.ly/2YczZzP
● Indirect Identity Control RFC: http://bit.ly/aries-rfc-103
● Appendix C of Sovrin Glossary: http://bit.ly/svrnglos-appC
● Sovrin Guardianship Task Force: http://bit.ly/svrn-guard-tf
● daniel.hardman@evernym.com
● @danielhardman on chat.hyperledger.org

Transparent vs. opaque guardians
Transparent
◦ Guardian is obvious in all or most
interactions.
◦ May be necessary to improve safety.
◦ Easy to audit.
◦ Less private for dependent and for
guardian.
Rover (pet). Unproﬁtable, Inc. Law ﬁrm resolving
affairs of someone recently deceased. Talent agent
for child pop star.
Opaque
◦ Guardian impersonates dependent.
◦ May be necessary to prevent discrimination
and hassle.
◦ Riskier to dependent and relying parties.
Limited auditability.
◦ More private for dependent and for
guardian.
Gayle (digital assiantance). Parent gives adult child
password, asks them to transfer funds on their death
to avoid probate court.

Modes of Guardianship
Holding-based
Dependent doesn’t have DIDs or a link secret, but credentials about the dependent are held
by the guardian. Guaranteed to be transparent because subject of credential is never the
holder.
Impersonation-based
Dependent has a link secret that guardian knows. Credentials can be issued where dependent
= subject, but creds are held by Guardian. DIDs and DID Docs can be created by guardian
using dependent’s link secret. Opaque unless forced into transparency.
Doc-based
Guardianship declared in DIDDoc to force transparency.

Holding-Based Guardianship
◦ Exists implicitly (parent holding a birth certiﬁcate, owner holding
pet license)
◦ Can be supplemented with an explicit guardianship credential
◦ Guardianship challenge can be answered with either explicit or
implicit proof
◦ Diffuse trust may be partly forced (e.g., both parents must
consent)
◦ Implicit creds as a basis introduce revocation problems
◦ Birth certiﬁcate may not be revoked if parental rights are
terminated
◦ Pet license may not be revoked when dog is sold

◦ Can be supplemented with an explicit guardianship credential
◦ Age proofs can force a guardian to break impersonation and share this -
improves safety!
◦ So can biometrics
◦ Not dangerous for controllership or delegation
◦ Adult dependents without biometrics have no real protections
◦ Revocation is a problem -- must be done in every relationship
◦ Use agent authz policy to prevent new relationships from forming?
Easy and doable today. Dangerous. Safeguards may need to be much higher in trust
framework (frequent challenges, biometrics required, etc.)
Impersonation-based Guardianship

{
"authorization": [
{"let":"#1", "do":"cred"}
]
}
Doc-Based Guardianship
Do a guardianship challenge
to find out what they can do.
DID Doc for dependent declares a key that belongs to guardian
and says, “Do guardianship challenge to evaluate authorization.”
Issue: must be done in every DID Doc (good and bad)
DID Doc of Dependent

Guardians often need to delegate
◦ Red Cross delegates work, some decisions for Mya to 1+ aid
workers
◦ Parent delegates to babysitter while they’re out of town
◦ Mom delegates digital assistance for grandma to teen
Solution: delegatable credentials

Ofﬂine operation
◦ Cached versions of trust framework and well-known schemas,
cred defs, issuers
◦ How fresh is guardianship challenge?
◦ Evaluate conﬂicting guardianship assertions without appeal or
research
◦ Save up audit reports for batch upload later
◦ Freshness of DID Doc knowledge

Revoking guardianship
Revoking guardianship cred can be done today, quickly and
efﬁciently.
Won’t be detected until next guardianship challenge.

Basis
◦ Basis for controllership could include:
◦ ownership
◦ delegation from owner
◦ court-appointed
◦ Basis for delegation is always someone who is in control
◦ Identity owner
◦ Controller
◦ Guardian
◦ Delegate

Delegatable Credentials
Hertz, Inc owns a car and, on the basis of that car, is its controller. Delegates limited
controllership to a local Hertz franchise. Fred rents the car and receives delegated
credential to control in more limited fashion. Fred drives the car to a fancy
restaurant and delegates even more limited controllership to valet parking.
Hertz Inc ⇶ franchise ⇉ Fred → valet
Each cred contains pre-proof of delegation. Validating requires checking revocation
status for each link on ledger, but no coordination among delegates.

Indirect Identity Control: delegation, guardianship, and controllership – Daniel Hardman

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Indirect Identity Control: delegation, guardianship, and controllership – Daniel Hardman