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Security Issues in Blockchained IoT

an anonymous node’s real-world identity. Any information relating to

private data of the user can be identified by an attacker; an intruder may

attempt de-anonymization of users by linking a user’s PKs (Primary Keys)

and ties to separate data pieces with the same anonymous user for a period.

• Modification Attack

The attacker must compromise the integrity of cloud storage to initiate

this attack. The attacker may then try to modify or delete stored infor­

mation for a certain user. This user can identify any improvements in the

storage data by matching the cloud hash with the local BC (Blockchain)

hash. When a user identifies a privacy infringement, he produces a transac­

tion implying two transactions: The user-signed transaction and the cloud

storage, which include the real method of the privacy and the user-signed

access transaction containing the database and the user-invalid hash of the

data. The transaction is then forwarded to many CHs (Cluster Heads) that

verify the initial transactions. In the event of incoherence of two hashes,

CH alerts the cloud storage nodes to malicious activities. However, when

subjected to this attack, the user cannot recover his data.

• Dropping Attack

The adversary will monitor a CH or group of CHs to launch this attack.

The CHs managed by the attacker will delete all transactions and blocks

that have been issued. Nonetheless, an intrusion will be observed because

of the lack of transactions or resources from the network from any nodes

belonging to the constituent clusters.

• Sybil Attack

A Sybil attack is a security vulnerability on an electronic infrastruc­

ture that aims to take over the network by the creation of several identi­

ties, nodes and machines. Attackers will deny the authentic nodes over the

network if appropriate false identities are generated and then fail to accept

or send blocks and obstruct other network users. Most Blockchains employ

different “algorithms of consensus” to better protect themselves against

Sybil attacks. These contain work proof, proof of stake and vicarious proof

of stake. Such algorithms of consensus do not eliminate attacks by Sybil,

but they render an effective attack by Sybil very impractical for an intruder.

3.4  APPLICATIONS OF BLOCKCHAINED IOT

There are numerous applications of Blockchain and IoT. The amalgamation of both

the technologies has come up with new possibilities. The following case studies can

be seen as the platforms where the amalgamated models can be used.

3.4.1  Case Study I: Smart Home Based on Blockchained IoT

A Blockchain-based smart home application is an example where this combined

technology can be seen. In IoT, security and privacy are the major concerns due to the

wide-ranging nature of IoT devices (Dorri et al., 2017). A large number of researchers