NotaryService(net: MessagingService, identity: Party, signingKey: KeyPair, uniquenessProvider: UniquenessProvider, timestampChecker: TimestampChecker)
A Notary service acts as the final signer of a transaction ensuring two things:
The (optional) timestamp of the transaction is valid
None of the referenced input states have previously been consumed by a transaction signed by this Notary
A transaction has to be signed by a Notary to be considered valid (except for output-only transactions w/o a timestamp)