Pablo has claimed that the use of blockchain technology for the MONS cryptocurrency will mean the cryptocurrency is both secure and scalable.

To what extent do you agree with Pablo?

Answers may include:

Security features

• All transactions are recorded into files called blocks.
• Each block contains a hash of the previous block as well as some transactions.
• Every transaction is visible to everyone, which makes it difficult to change existing data which may be replicated on thousands of computers (decentralization).
• Any change to any historic transaction would be noticeable because the hashes of all subsequent blocks would not agree.
• Transactions are confirmed many times (consensus control).
• The more users of MONS there are, the more likely that there will be additional miners, which will increase the security of the network.
• A proof of work is required when creating a new block, which makes the effort required to falsify many blocks unfeasible (intractable).
• Each user has his own private key which is unknown to anyone else, as well as a public key (cryptography).
• With no central authority there is no focus point for hackers to attack.
• As MONS uses a private blockchain then only verified and approved computers could mine;
• The larger and more distributed the network is, the safer it is considered to be.

Security concerns

• Ledgers are technically not immutable (but to do so would require unfeasible computing power and taking over >51% of the network within the space of 10 minutes (ie a 51% attack).
• The 51% attack is more likely to be successful on a small private blockchain rather than a large public one.
• Attacks on cryptocurrencies have been documented (reference opportunities).
• These attacks related to access to wallets (obtaining private keys).
• Currency transfer websites are a target and have been hacked with cryptocurrencies stolen.
• With no central control it is difficult to rollback transactions.
• DDoS attacks on cryptocurrency services may slow transactions slightly/may affect MONS value.
• Future concerns have been expressed about the scalability of the blockchain, lack of standards, and how it can be used if laws on data privacy become tighter.

Scalability

• Scalability is defined as the capacity for a system or network to grow in size to manage increased demand.
• Thus, scalability refers to the ability of the MONS currency to continue to function when the number of transactions increases.
• Number of miners are likely to increase in proportion to the number of transactions because there are more rewards.
• A peer-to-peer network makes scalability possible because it is easy to add new nodes.
• A peer-to-peer network is unlikely to bottleneck with increased transactions.
• An increase in processing speeds for miners causes the nonce difficulty level to adjust and allows the blockchain to function (regardless of the number of miners).
• Due to the limitations of proof of work, blocks should take a minimum time (e.g. 10 minutes) to create and should hold in the region of 1MB of data, which is about 1000 to 3000 transactions.
• Other consensus methods can be used to increase scalability at a slight cost of decentralization, e.g. using proof of stake, proof of ownership, instead of PoW;
• However, if the network becomes heavily congested, a MONS currency transaction might take longer to be processed.
• If a network is running slowly, the mining fees have to increase or there is a risk that miners will stop mining.
• These increased fees will need to be paid by the users making a cryptocurrency transfer. Small cryptocurrency transfers may incur high charges making the currency undesirable.
• Blockchain ledgers are more scalable than centralized ledgers because they are distributed and there is no bottleneck.

Strategies to improve scalability include
Increasing the block size to include more transactions.

• The initial reason behind block size limits is to prevent Denial-of-Service (DOS) attacks by hackers seeking to create huge (or infinite) blocks that would harm and paralyze the blockchain.
• Increasing the block size to cope with increased demand may place the MONS currency at a risk of attack.

Modifying the underlying protocol (although the issue with this is that there needs to be some central governance to make these decisions).

• The code is open source and a consensus (proposal and voting on forums and discussions boards) would be need to change the protocol.
• Since its creation there have been very few changes to the bitcoin source code so is unlikely that MONS blockchain code would be open to frequent changes.
• In Santa Monica, the MONS project would need some form of governance so that decisions to change the protocol and improve scalability could be made.

Sharding and other “Layer 2” solutions can be implemented to reduce congestion on blockchains, in which slower transaction types are put on a different chain which deals only with that type.
For example, Lightning networks, which is a layer 2 payment protocol designed to be layered on top of a blockchain-based cryptocurrency.

Security could be optimized according to the "Blockchain Trilemma".

Scalability concerns

• The lack centralized servers means that there is no control over the amount of hardware that can be added to the system (i.e. if centralized, scalability could be improved by the central authority by adding more processing power).
• Making decisions / governance of a distributed ledger is more difficult and has to rely on voting and an agreement before proceeding.
• The increased network traffic of many nodes on the blockchain can have a greater overall requirement for network bandwidth than (for example) centralized miners.
• Scalability in distributed ledger systems such as blockchain depends on the participation of the whole network, whereas centralized ledger systems (for example VISA) which depend only on the service provider and can scale quickly, but with hard limits imposed by the infrastructure.

Conclusion
A reasonable conclusion that includes both security and scalability.

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