OpenID Shared Signals Framework: Giving Identity Systems a Way to Talk to Each Other

There is a fundamental problem with modern identity systems that is easy to overlook.

Authentication tells a service who you are.

Authorization tells a service what you are allowed to do.

But, neither necessarily tells another service that something has changed. These are discrete, static events. They periodically reoccur within the context of a user’s session, but there is time between those events where current state changes are not communicated.

• A user may have just changed their password.
• A security team may have determined that an account has been compromised.
• An administrator may have disabled an account.
• A session may have been revoked.
• A device may have fallen out of compliance.
• A risk engine may have determined that an authentication event that was perfectly acceptable ten minutes ago is no longer acceptable.

In a traditional architecture, every application has to discover those changes for itself.

That is where the OpenID Shared Signals Framework (SSF) comes in.

SSF provides a standardized way for cooperating systems to exchange security-related events and signals. Rather than requiring every application to independently poll every identity provider, security service, or other system for changes, SSF establishes a framework for sending those changes between Transmitters and Receivers.

The result is a mechanism in which when something important changes, tell the systems that need to know.

And, although the mechanism is based on HTTP, JSON, JWTs, and existing IETF security-event standards, the architectural implications are considerably larger.

The Problem SSF Is Trying to Solve

Consider a relatively ordinary enterprise environment.

There might be:

The Identity Provider (IdP) knows things about users that the other systems may not know.

For example:

User account disabled Password changed Account compromised MFA reset Session revoked

Meanwhile, other systems may have information of their own:

Device compromised Malware detected Risk increased Session suspicious Application access revoked

Without a standardized signaling mechanism, each integration tends to become its own API.

That produces a familiar enterprise problem:

The individual integrations may work perfectly well.

The problem is what happens when there are hundreds of them.

SSF provides a common model for these interactions.

What Is a “Signal”?

A signal is essentially information about a security-relevant change.

The distinction between a signal and an ordinary API response is important.

An API might answer what is the current state of this user?

A signal can instead state that something happened that you should know about.

That makes SSF particularly useful for systems that need to react to changes rather than continually asking for the current state.

For example:

The consuming systems can then take whatever action is appropriate.

• Perhaps they terminate sessions.
• Perhaps they require reauthentication.
• Perhaps they increase authentication requirements.
• Perhaps they disable access entirely.

SSF itself generally isn’t making that authorization decision.

It is providing the signal that allows another system to make the decision.

That distinction is fundamental.

Transmitters and Receivers

SSF introduces two primary roles.

Transmitter

The Transmitter produces security events.

For example:

A Transmitter might know that user@example.com has experienced a particular security event.

The transmitter is responsible for communicating that event through an SSF event stream.

Receiver

The Receiver consumes those events.

For example:

The receiver determines what to do with the information.

This creates an important separation of responsibility.

SSF provides the communication mechanism.

The receiver’s security policy determines the response.

Event Streams

One of the central concepts in SSF is the Event Stream.

Rather than simply firing arbitrary webhooks at arbitrary endpoints, SSF defines mechanisms for establishing and managing streams of security events.

A receiver can establish a stream with a transmitter and specify the events it is interested in.

Conceptually:

The stream can also be managed.

SSF defines mechanisms for operations such as:

Create stream Update stream Pause stream Resume stream Delete stream

This makes SSF more than a standardized webhook format.

It provides a framework for managing the relationship between the systems exchanging security signals.

Push or Poll?

SSF supports both push and polling models.

With push delivery, the transmitter sends events to an endpoint provided by the receiver.

With polling, the receiver retrieves events from an endpoint provided by the transmitter.

This matters because different environments have different networking and operational requirements.

A cloud service that can accept inbound HTTPS traffic might prefer push.

An environment with restrictive inbound connectivity might prefer polling.

SSF doesn’t require every deployment to use exactly the same transport behavior.

SSF and Security Event Tokens

This is where SSF connects to another important IETF standard.

SSF uses the Security Event Token (SET) defined by RFC-8417 as the container for security events.

A SET is a JWT containing an event.

Conceptually:

A simplified event might look conceptually like:

{ “iss”: “https://idp.example.com”, “jti”: “unique-event-id”, “iat”: 1720000000, “aud”: “receiver.example.com”, “events”: { “some-event-type”: { “…” } } }

The actual SSF event structure contains considerably more detail, including subject identification and event-specific information.

The important point is that SSF isn’t inventing an entirely new security-token ecosystem.

It builds on existing IETF Security Events work.

The SSF specification specifically profiles SET and the HTTP delivery mechanisms defined by the IETF.

The Subject Is Just as Important as the Event

Knowing that something happened isn’t particularly useful unless you know what it happened to.

SSF therefore has a concept of a subject principal.

For example, an event might concern:

• A human user
• A device
• A session
• An application
• A resource

The subject identification mechanism is deliberately more flexible than simply assuming that every event is about a JWT sub claim.

In fact, SSF explicitly requires that the ordinary JWT sub claim not be used in SSF SETs, with the subject represented using the SSF subject mechanisms instead.

That distinction becomes important in distributed environments.

The identifier that one system uses for a person may not be the identifier another system uses.

SSF, therefore, needs a way to describe subjects without assuming that every participating system has adopted exactly the same identifier namespace.

Discovery

A receiver needs to know how to communicate with a transmitter.

SSF defines configuration metadata and a discovery mechanism for obtaining it.

A transmitter supporting discovery exposes configuration information through:

/.well-known/ssf-configuration

The metadata describes information that a receiver needs in order to interact with the transmitter, including information about supported capabilities and stream-management endpoints.

Conceptually:

This is an important part of the design.

Standards become much easier to integrate when the protocol doesn’t require administrators to manually exchange every endpoint and configuration parameter.

The discovery mechanism gives the receiver a standardized starting point.

Authentication and Authorization

There is another subtle but important point.

SSF defines the framework for exchanging signals, but it does not mandate a single SSF-specific authentication and authorization mechanism for securing its management APIs.

Instead, the framework allows the cooperating parties to use an appropriate authorization mechanism.

OAuth2 is one possibility.

For example:

This is consistent with the broader philosophy of SSF.

The framework defines the semantics of the security-event relationship while allowing deployments to use appropriate security mechanisms for protecting the underlying HTTP interfaces.

The Event Itself Is Not the Policy

This is perhaps the most important architectural distinction.

Suppose a transmitter sends:

Account compromised

SSF doesn’t inherently say:

Terminate every session immediately.

Instead:

Each receiver can interpret the signal according to its own security requirements.

One application might terminate the session.

Another might require MFA.

A third might temporarily restrict access.

This is why it is useful to think of SSF as a signaling layer, not an authorization engine.

Where CAEP Fits

SSF becomes particularly powerful when combined with the Continuous Access Evaluation Profile (CAEP).

CAEP defines event types intended for communicating changes that can affect access decisions.

For example, a receiver may need to know that:

• A session has changed
• A credential has changed
• A user has been disabled
• A risk condition has changed

The goal is to move beyond the traditional model:

and toward:

This is the “continuous” part of Continuous Access Evaluation.

CAEP is a profile built on SSF, defining event types that allow transmitters and receivers to communicate changes that can affect access to users, devices, sessions, and applications.

Where RISC Fits

SSF also provides the foundation for Risk Incident Sharing and Coordination (RISC).

RISC addresses a related problem.

Suppose, an identity provider discovers that an account has been compromised.

The identity provider may want other participating services to know.

Instead of creating a completely separate event-sharing protocol, RISC defines event types using the SSF framework.

The architecture therefore looks roughly like:

This is one of the strengths of the design.

SSF provides the common signaling infrastructure.

Profiles such as CAEP and RISC define particular categories of events and use cases.

The OpenID Foundation describes these as separate specifications built on the Shared Signals framework.

Why This Is Different From Token Expiration

A common way of dealing with changing security conditions is to make access tokens short-lived.

For example,

That reduces the amount of time a compromised token remains useful.

But, it doesn’t provide immediate notification.

Suppose, a user’s account is compromised one minute after the token is issued.

The relying application might not discover that fact until the token expires.

SSF provides another mechanism:

The difference is between periodic expiration-based control and event-driven security response.

They aren’t mutually exclusive.

A well-designed system can use both.

SSF Is Essentially a Security Event Bus

One useful way to think about SSF is as a standardized security-event bus between organizations and systems.

Imagine:

The transmitter doesn’t need to know exactly what every receiver will do.

The receiver doesn’t need to continuously query every transmitter.

The shared protocol provides a common language for security events.

That is a significant architectural improvement over a collection of proprietary integrations.

Privacy Matters Too

Security-event sharing inevitably raises a privacy question. How much information should one system tell another system?

SSF explicitly addresses this issue.

A transmitter should only share information that is appropriate for the event and relationship.

The specification includes privacy considerations around subject information and consentable data. In particular, where a transmitter intends to include data that has not already been consented to for release, the transmitter must obtain appropriate consent in accordance with its privacy policy.

This is important because security systems can contain extremely sensitive information.

A useful security architecture should not turn Security Event A into Everything we know about this person

The event should contain the information necessary for the receiving system to act.

Nothing more.

SSF Does Not Replace Existing Identity Protocols

It is also important not to misunderstand where SSF sits in the identity stack.

SSF isn’t a replacement for:

• OAuth2
• OpenID Connect
• SAML
• SCIM
• FIDO/WebAuthn

It addresses a different problem.

A simplified identity architecture might look like:

SSF adds another dimension:

The first set of protocols helps establish identity and access.

SSF helps communicate changes in security state.

That distinction is increasingly important as organizations move toward distributed architectures.

A Concrete Example

Consider an employee who has access to ten SaaS applications.

At 9:00 AM:

At 10:17 AM, the security team discovers that the employee’s credentials have been compromised.

Without shared signaling, the organization might need to contact each application independently.

With SSF, an appropriate security event can be transmitted:

Each receiver can then apply its own policy.

For example:

The identity system doesn’t have to implement the internal security policy of every application.

It simply provides the signal.

The Standardization Matters

There is nothing particularly revolutionary about sending a webhook.

Organizations have been doing that for years.

The value of SSF is in standardizing the semantics, structure, discovery, stream management, subjects, and delivery mechanisms around security events.

The difference is important.

A proprietary webhook might tell you:

{ “event”: “userBad” }

Another vendor might use:

{ “type”: “COMPROMISED_ACCOUNT” }

Another might send:

{ “risk”: “critical” }

Even if all three systems are describing approximately the same thing, integrating them requires custom logic.

Standards provide common semantics.

That allows an ecosystem of independent implementations to communicate without requiring every pair of vendors to negotiate a private protocol.

SSF Became a Final Specification

The Shared Signals work has been progressing for several years.

The framework originally appeared as the Shared Signals and Events Framework, before the name was shortened to the Shared Signals Framework. The work subsequently produced the CAEP and RISC profiles as well.

In September 2025, the OpenID Foundation announced that its membership had approved the OpenID Shared Signals Framework 1.0, along with OpenID CAEP 1.0 and OpenID RISC 1.0, as Final Specifications.

That is an important milestone.

These aren’t merely ideas being discussed in an identity conference.

They are standardized building blocks intended to support interoperability between real identity and security systems.

And, the Iya-STS and Identity Protocol Debugger supports all three.

Summary

Modern authentication systems have become very good at answering, “Who are you?”

Authorization systems have become very good at answering, “What are you allowed to access?”

But, modern security increasingly needs to answer another question, “Has anything changed since we made that decision?”

That’s where Shared Signals becomes important.

• A user can be authenticated and still become risky.
• A session can be valid and still need to be terminated.
• A device can be trusted and subsequently become compromised.
• A credential can be legitimate and subsequently be revoked.
• A security decision is therefore not necessarily something that should be made once and forgotten.

It may need to be reconsidered as new information becomes available.

SSF provides a standardized mechanism for distributing that information.

The architecture is ultimately quite straightforward:

The important innovation isn’t the HTTP POST.

It isn’t the JWT.

It isn’t even the event itself.

The important idea is that security state can be communicated continuously between independently operated systems.

That gives identity architectures something they have historically lacked: a standardized way to react when the assumptions behind an existing access decision stop being true.

Authentication establishes a fact.

Authorization makes a decision.

Shared Signals provides a mechanism for communicating when the facts have changed.

And, in an environment where identity, applications, devices, sessions, and security controls are increasingly distributed across organizational boundaries, that ability to communicate may be just as important as the original authentication itself.

Notes

• AI / GenAI / ChatGPT / etc were not used to generate the text of this article.
• ChatGPT was used to generate the images.
• I used em dashes in my writing before the current GenAI wave was a thing. Not planning on changing now.
• Names have been changed to protect the guilty.
• None of the hostnames or users used in examples actually exist.
• Feel free to post any comments or suggestions below.
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• Do not attempt to use any ideas, code, or programs discussed here in a production environment without first testing it in a non-production environment.
• I’m not responsible for the spontaneous combustion of the known universe or anything else bad that happens to you today as a result of your having read this blog post.