cosmos-sdk/x/evidence/spec/01_concepts.md

Concepts

Evidence

Any concrete type of evidence submitted to the x/evidence module must fulfill the Evidence contract outlined below. Not all concrete types of evidence will fulfill this contract in the same way and some data may be entirely irrelevant to certain types of evidence.

type Evidence interface {
  Route() string
  Type() string
  String() string
  Hash() HexBytes
  ValidateBasic() error

  // The consensus address of the malicious validator at time of infraction
  GetConsensusAddress() ConsAddress

  // Height at which the infraction occurred
  GetHeight() int64

  // The total power of the malicious validator at time of infraction
  GetValidatorPower() int64

  // The total validator set power at time of infraction
  GetTotalPower() int64
}

Registration & Handling

The x/evidence module must first know about all types of evidence it is expected to handle. This is accomplished by registering the Route method in the Evidence contract with what is known as a Router (defined below). The Router accepts Evidence and attempts to find the corresponding Handler for the Evidence via the Route method.

type Router interface {
  AddRoute(r string, h Handler) Router
  HasRoute(r string) bool
  GetRoute(path string) Handler
  Seal()
  Sealed() bool
}

The Handler (defined below) is responsible for executing the entirety of the business logic for handling Evidence. This typically includes validating the evidence, both stateless checks via ValidateBasic and stateful checks via any keepers provided to the Handler. In addition, the Handler may also perform capabilities such as slashing and jailing a validator.

type Handler func(Context, Evidence) error