indirect mode

Definition

Two primary trust modalities motivated the KERI design, One these is the indirect (one-to-many) mode, which depends on witnessed key event receipt logs (KERL) as a secondary root-of-trust for validating events. This gives rise to the acronym KERI for key event receipt infrastructure.
The indirect mode extends that trust basis with witnessed key event receipt logs (KERL) for validating events. The security and accountability guarantees of indirect mode are provided by KA2CE or KERI’s Agreement Algorithm for Control Establishment among a set of witnesses.
Source: Abstract KERI white paper

Operational mode

To protect a validator when engaging with some other controller’s identifier, be it verification, control authority establishment, or duplicity detection, are based on an ability to replay the sequence of key events (key event history or log) of that identifier. There are two main operational modes for providing replay capability that are distinguished by the degree of availability of the identifier’s controller when creating and promulgating the key events.
With indirect mode, the promulgation of events to a validator may happen even when the controller is not attached to the network and therefore not able to communicate directly with a validator. Indirect mode supports high (nearly continuous) availability of the key event history to any validator. This means that other components must be trusted to promulgate key events when the controller is not attached to the network. Indirect mode is compatible with identifiers for one-to-many exchanges or any-wise relationships (a controller with any others). A single indirect mode identifier may be used for a public service or business or otherwise when building brand and reputation in that identifier is important. An indirect mode identifier may also be used for private one-to-one or select groups but where intermittent availability is not tolerable.
More in Source: chapter Protocol Operational Modes in KERI white paper

Security concerns

The protocol may operate in two basic modes, called direct and indirect. The availability and consistency attack surfaces are different for the two modes and hence the mitigation properties of the protocol are likewise mode specific. Source: chapter Security concerns in KERI white paper

Also see

Direct mode