  This paper considers an Internet of Thing (IoT) blockchain network consisting
of a leader node and various follower nodes which together implement the RAFT
consensus protocol to verify a blockchain transaction, as requested by a
blockchain client. Further, two kinds of active attacks, i.e., jamming and
impersonation, are considered on the IoT blockchain network due to the presence
of multiple {\it active} malicious nodes in the close vicinity. When the IoT
network is under the jamming attack, we utilize the stochastic geometry tool to
derive the closed-form expressions for the coverage probabilities for both
uplink and downlink IoT transmissions. On the other hand, when the IoT network
is under the impersonation attack, we propose a novel method that enables a
receive IoT node to exploit the pathloss of a transmit IoT node as its
fingerprint to implement a binary hypothesis test for transmit node
identification. To this end, we also provide the closed-form expressions for
the probabilities of false alarm, missed detection and miss-classification.
Finally, we present detailed simulation results that indicate the following: i)
the coverage probability improves as the jammers' locations move away from the
IoT network, ii) the three error probabilities decrease as a function of the
link quality.
