The localhost client handles state verification through the ClientState interface methods VerifyMembership and VerifyNonMembership by performing read-only operations directly on the core IBC store. When verifying channel state in handshakes or processing packets the 09-localhost client can simply compare bytes stored under the standardized key paths defined by ICS-24. For existence proofs via VerifyMembership the 09-localhost client will retrieve the value stored under the provided key path and compare it against the value provided by the caller. In contrast, non-existence proofs via VerifyNonMembership assert the absence of a value at the provided key path. Relayers are expected to provide a sentinel proof when sending IBC messages. Submission of nil or empty proofs is disallowed in core IBC messaging. The 09-localhost light client module defines a SentinelProof as a single byte. Localhost client state verification will fail if the sentintel proof value is not provided.
var SentinelProof = []byte{0x01
}