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Blockchain Technology

registered with the cluster head, then the transaction will not be transferred

in the network and accelerated to other clusters.

• Distributed DOS (DDoS) Attack

DDoS attacks render certain facilities inaccessible by overwhelm­

ing them with unnecessary counterfeit traffic. The traffic uses space and

energy, such that the platform is shut down. Mainly due to a lack of ade­

quate security features for connected IoT devices, the potential for disrup­

tion and the choice of manufacturing costs and profit potentials have been

under-estimated in the past. However, recent events have triggered a rethink

to include and promote safety characteristics for connected products as part

of a premium positioning. Now, it may not be simple for a professional

intruder to manipulate IoT devices and build a botnet.

• 51% Attack

A specific weakness in Blockchain implementations is the 51% attack,

where the hash rate of the network bulk for accessing the database is

obtained by one intruder, a community of Sybil nodes or a mining pool

on the network. Attackers would avoid confirmation of new transactions,

which would allow them to stop transactions between some or all users. In

rare circumstances, attackers with a hash rate of over 50% can take other

miners and add their blocks with a high likelihood to the Blockchain; in

addition, fraudulent or double-spent transactions may occur.

• Double-Spending

Whether twice or on many occasions, double-spending involves the

usage of a onetime transaction. A transaction moves asset ownership from

the identity of a sender to the public address of the receiver, and the signa­

tory is required to sign the transaction using a private key. After the trans­

action has been signed, it will be transmitted to the network on which the

transaction is validated. The receiver searches for the sender’s unexpended

transaction, searches the signature of the sender and assumes that a transac­

tion is mined in a legitimate chain.

• Mining Attack

In this attack, a few cluster heads are hacked by an adversary, who starts

manipulating several of them; false mining is possible in such a situation,

but if other cluster heads or nodes detect it, they can easily track the false

cluster heads. If the network senses a false cluster head, it can be altered by

the nodes in that cluster.

• Collision Attack

A collision attack on an authenticated hash attempts to trigger a hash

collision, that is, two inputs of the same hash value. If an attacker succeeds,

this could generate two public keys with the same address. The intruder

does not monitor the content of any message during a classical collision

attack; it is randomly chosen by the algorithm.

• Linking Attack

An attacker, who could be a cloud storage or service provider, connects

several cloud data or Blockchain transactions with the same ID to establish