The document discusses key concepts related to identity systems, including subjects, relying parties, attributes, and the basic functions of an identity provider. It outlines a basic identity system model where the identity provider authenticates the user and authorizes the release of attributes to relying parties. It also covers important topics such as user trust, authentication methods, credential management, directed identity, attribute sources, and security and availability challenges.

1. Identity Systems
Jim Fenton

2. “Defining identity is
like nailing Jell-O®
to the wall.”
– Source Uncertain
Flickr photo by stevendepolo
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3. Terminology
 Subject
The person (usually) whose identity is involved
Sometimes called the User
 Relying Party
The entity the Subject is interacting with
Sometimes called the Service Provider
 Attribute
A piece of information about the Subject
Sometimes called a Claim
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4. A Basic Identity System
Government
Identity
Provider
Authentication
Request
Commerce
Social Media
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5. A Basic Identity System
Government
Identity
User
Provider
User Credentials
Authentication
Commerce
Social Media
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6. A Basic Identity System
Government
Identity
Authorize Info
Provider
Attribute Request/
Release Response
Commerce
Social Media
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7. Elements of Identity Management
Percent
Authentication Credential Management
Establish who the Subject is Prove to Relying Parties
who the Subject is
Attribute Management
Provide information about
the Subject
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8. User Trust
 User trust in their Identity Provider is fundamental
Not all users trust any one entity
Most likely to trust entities they do business with and
strong, trusted brands
Different trusted entities in different cultures
 An ecosystem of identity providers is required
Users need to choose their own identity provider
Need to consider ability to migrate to a different provider if
required
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9. Authentication
Flickr photo by shannonpatrick17
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10. Authentication Methods
 Methods useful for user authentication are
situation-specific
Type of endpoint being used
Required authentication strength (transaction value, etc.)
 Problem: Many existing identity systems are bound
tightly to specific authentication methods
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11. Authentication Strength
 Authentication strength should depend on
transaction value
iTunes purchase (99 cents) vs. vehicle purchase
 NIST Special Pub 800-63 defines 4 levels:
Level 1: Minimal challenge/response
Level 2: Single-factor identity proofing
Level 3: Multi-factor identity proofing
Level 4: Hardened multi-factor
 Relying party specifies the required strength to the
identity management system
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12. Authentication Endpoint Diversity
 The Web is pervasive, but not everything is a
browser
 Examples
Vending Machines
Set-top boxes
Doors (physical security)
 Modular approaches to authentication needed to
consider a wide range of use cases
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13. Security Opportunities
 Users that authenticate frequently at a given service
are more likely to detect anomalies
More likely to be suspicious about, for example, lack of a
certificate
Browsers can be configured to specially flag “chosen”
identity providers
 Identity providers can detect anomalous user
behavior
Similar to detection of fraudulent credit card transactions
Business/policy framework should encourage this
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14. Credential
Management
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15. Credential Management: Functions
 Act as a “key cabinet” for the user
Each relying party has its own credentials
 Support Directed Identity
Prevent undesired release of correlation handles
Identifiers to Relying Parties are opaque by default
 Enforce secure use of credentials
Require use of secure channel (e.g., SSL)
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16. Directed Identity
 It should not necessarily be possible for different
Relying Parties to correlate identifiers
Insurance company vs. supermarket account
Pseudonymous identifiers for tip hotlines
 Users may still choose to link relying parties’
identifiers
 Attributes may also provide correlation handles
 Credential manager can be subpoenaed if
appropriate
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17. Security and Availability Issues
 Security
The credential store is a very high-value target
Credentials can be distributed to diffuse attack
High-level physical security is also required
 Availability
Failure of an Identity Manager may have severe impact on
its Subjects
Solvable problem, but needs to be addressed
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18. Attribute
Management
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19. Distributed Attributes
 Self-asserted attributes have limited utility
 Authoritative sources for different attributes come
from different places
FICO scores from a credit bureau
Driving record from state Motor Vehicle Department
Proof of employment from employer
 Identity system has a role in locating trustable
sources of attributes
 Attributes delivered as signed assertions
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20. Attribute Distribution: Example
Healthcare
Provider
Identity
Provider
Authorization “Is subject 21?” Request
Request
Wine Merchant
Motor Vehicle
Department
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21. Attribute Distribution: Example
Healthcare
Provider
Identity
Provider
Release Trust Negotiation
Authorization
Wine Merchant
Motor Vehicle
Department
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22. Attribute Distribution: Example
Healthcare
Provider
Identity
Provider
“Is subject 21?”
Request
Wine Merchant
Motor Vehicle
Department
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23. Attribute Distribution: Example
Healthcare
Provider
Identity
Provider
“Subject is 21 or over”
–DMV Wine Merchant
Motor Vehicle
Department
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24. Attribute Trust
 Federation: Prearranged trust relationships
Personnel Security Clearances among Federal agencies
Business partners
 Accreditation: Indirect federation
Financial institutions, schools
Scales much better than direct federation
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25. Identity Provider Trust
 Identity Provider has a fiduciary responsibility
 To the Subject:
Must use credentials only for the proper Subject
 To Relying Parties:
Must associate attribute requests and responses reliably
 Identity Provider may coincidentally function as an
Attribute Provider
Functions should be considered separate to maintain
privacy
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26. Summary
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27. Observations
 Scaling is critical
Technical (protocol) aspects of scaling are a solved
problem
Scaling of trust relationships is the real limitation
 Chosen technologies need to consider a very wide
range of use cases
 An ecosystem of identity and attribute providers is
needed
Need business models for these functions
Public policy should encourage constructive behavior and
help these entities manage liability exposure
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