*1.2.3 Resistance to double spending attacks*

The double-spending attack in the context of the bitcoin blockchain refers to a specific problem unique to digital currency transactions. It should be noted that the double-spending attack can be considered a general security problem due to the fact that digital information can be replicated relatively easily. Specifically, in digital token exchange transactions, such as electronic money, there is a risk that the holder will duplicate the digital token and send multiple identical tokens to multiple recipients. If inconsistency can be incurred due to duplicate digital token transactions (e.g., spending the same bitcoin token twice), then the problem of double spending becomes a serious security threat. To prevent duplication, bitcoin evaluates and verifies the authenticity of each transaction using the transaction logs on its blockchain with a consensus protocol. By ensuring that all transactions are included in the blockchain, in which the consensus protocol allows everyone to publicly verify the transactions in a block before committing the block to the global blockchain, this ensures that the sender of each transaction only spends the bitcoins he or she legitimately owns.

*Methodology of the Blockchain Monitoring Framework DOI: http://dx.doi.org/10.5772/intechopen.109550*

In addition, each transaction is signed by its sender using a secure digital signature algorithm. This ensures that if someone forges the transaction, the verifier can easily detect it. The combination of transactions signed using digital signatures and public verification of transactions using majority consensus ensures that the blockchain can withstand the double-spending attack [11].

### *1.2.4 Defying the attacks of the majority consensus (51%)*

A 51% attack is an attack that targets the so-called Proof of Work (PoW) or Proof of Stake (PoS) blockchains.

This attack refers to the risks of cheating in the majority consensus protocol. One of these risks is often referred to as the 51% attack, particularly in the context of double spending.

An example of a 51% attack can occur if one cooperative becomes too large relative to the others, which can allow for a 51% attack, when they agree to carry out a conspiracy, such as in vote counting or illegally transferring cryptocurrencies to one or more target wallets, reversing authentic transactions as if they never happened, etc.

Today, measures have been taken on large-scale blockchains like bitcoin to resist this type of attack, but it is still exploitable.

#### *1.2.5 Resistance to OWASP*

The Open Web Application Security Project (OWASP) is an online community working on web application security [12]. While OWASP's top ten vulnerabilities list is designed to describe vulnerabilities faced by web application developers, nine of OWASP's ten vulnerabilities also apply to blockchain systems. Even though the blockchain ecosystem has been designed to solve most of the security issues faced in web application and information system design due to the use of advanced cryptographic mechanisms and 51% consensus in blockchain, it is worth noting that the avenues for monitoring remain unexplored, and it is worth considering the possibilities of investigating the implementation of the blockchain monitoring mechanism (**Table 1**).


#### **Table 1.**

*OWASP Top 10 application security risks—2017 and blockchain resistance [12].*
