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Subject identifiers#

Subject identifiers(defined in OpenID Connect Core SPEC) are unique identifiers generated by Janssen Server(i.e. OpenId Provider) for an end-user. Subject identifiers are unique per Janssen Server instance and it is shared with the client (or clients) via ID token or access token. Whether the same subject identifier is used for the same end-user across multiple clients depends on the kind of subject identifier configured for a particular client.

Types of Subject Identifiers#

Janssen Server supports both subject identifier types, public and pairwise, as specified in OpenID Connect specification. For a particular Janssen Server deployment, the supported types are listed in the response of Janssen Server's well-known configuration endpoint is given below.

The subject_types_supported claim in the response specifies the list of all the supported types.

More details about both types are given in this section of specification.

Public Subject Identifiers#

Public subject identifiers are identifiers that the server generates and assigns to each subject. These identifiers are unique for each server deployment. All the clients that are configured to use a public type subject identifier will be supplied this same identifier for a given subject by the Janssen Server.

Sharing common subject identifiers across multiple clients may enable clients to correlate data about a particular subject. If this is an unwanted situation, then the client should use pairwise subject identifiers.

By default, the Janssen Server uses the subject attribute inum as the subject identifier.

Customizing Subject Identifier Attribute#

At the server level, the administrator specifies which subject attribute should be used as subject identifiers. This can be done by updating the value of openidSubAttribute Janssen Server property.

At the client level, this can be further customized. If a client uses public type subject identifier, the client can configure the subject attribute that should be used as a subject identifier. This should be done at the client registration time.

To enable client level customization, the Janssen Server property publicSubjectIdentifierPerClientEnabled should be set to true and also the desired attribute should be part of the list defined by the Janssen Server property subjectIdentifiersPerClientSupported. Both these properties can be set by the administrator using TUI.

Pairwise Subject Identifiers#

When a client chooses to use pairwise subject identifier, the Janssen Server generates and attaches a new identifier to all the subjects requested by the client. This identifier is consistently used for the subject-client pair and never used for any other clients configured on the Janssen Server. If multiple clients are using pairwise type subject identifiers, then the same subject will have different identifiers for each subject.

Since every client has a different identifier for the same subject, the clients can't match identifiers and correlate information about a subject out of the band.

Pairwise Identifier Generation#

Janssen Server uses host name string from redirect URI or sector identifier, local user ID, and a salt string as initial inputs to generate pairwise identifiers. This input is then signed with the HS256 signing algorithm to generate a pairwise identifier.

Sector identifier configuration influences how pairwise identifiers are calculated. See this document for more details.


Janssen Server allows customization concerning subject identifiers using the properties below:

Want to contribute?#

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Last update: 2023-08-03
Created: 2022-07-21