  The design of permissioned blockchains places an access control requirement
for members to read, access, and write information over the blockchains. In
this paper, we study a hierarchical scenario to include three types of
participants: providers, collectors, and governors. To be specific, providers
forward transactions, collected from terminals, to collectors; collectors
upload received transactions to governors after verifying and labeling them;
and governors validate a part of received labeled transactions, pack valid ones
into a block, and append a new block on the ledger. Collectors in the
hierarchical model play a crucial role in the design: they have connections
with both providers and governors, and are responsible for collecting,
verifying, and uploading transactions. However, collectors are rational and
some of them may behave maliciously (not necessarily for their own benefits).
In this paper, we introduce a reputation protocol as a measure of the
reliability of collectors in the permissioned blockchain environment. Its
objective is to encourage collectors to behave truthfully and, in addition, to
reduce the verification cost. The verification cost on provider $p$ is defined
as the total number of invalid transactions provided by $p$ and checked by
governors. Through theoretical analysis, our protocol with the reputation
mechanism has a significant improvement in efficiency. Specifically, the
verification loss that governors suffer is proved to be asymptotically
$O(\sqrt{T_{total}})$ ($T_{total}$, representing the number of transactions
verified by governors and provided by $p$), as long as there exists at least
one collector who behaves well. At last, two typical cases where our model can
be well applied are also demonstrated.
