As previously stated, there are many different cryptocurrencies whose protocols are very similar to that of Bitcoin. There are several major areas in which these protocols typically differ.A. Proof of Work vs. Proof of Stake Proof of work means that the probability of “mining” a block is proportional to the processing work done by the miner. In a group of miners, coins in a proof-of-work system are divided based on their “hashrates,” or the number of hash attempts they can make per second. As previously stated, Bitcoin uses a proof-of-work system. Proof-of-stake systems differ from proof-of-work systems because processing power does not matter for the probability of mining a block. Instead, the probability is based on the number of coins the miner owns. So, if a miner owns 1% of the existing coins, he can mine 1% of the blocks. Coin owners then become a “stakeholder” of sorts, having more mining power when they hold more stakes. Proof of stake is often considered an improvement over proof of work for two main reasons. The first is due to lower transaction fees in the long run. If rewards are only paid with transaction fees in a proof-of-work system, miners can demand a minimum transaction fee as a reward for spending resources. Proof of Stake discourages this, because solving blocks requires no physical resources. The second reason why Proof of Stake has an advantage over Proof of Work is that it reduces the likelihood of a specific type of attack called a 51% attack, which involves an attacker controlling more than 50% of processing power. (we'll talk about this later). Proof of stake reduces the likelihood of this happening, because instead of having to own the majority of the processing power, you would have ...... middle of paper ......ctions that they process. If enough blocks were to be added to this competing chain, it would take over from the main chain and attackers would be able to collect the majority of the rewards for hashing the blocks. More importantly, it would allow attackers to spend their coins twice, as they could effectively reverse the transaction and let the coins be spent again. Cryptocurrencies could combat this by ensuring that mining pools make up no more than 25% of the network [13].VII. CONCLUSIONFiat currencies are starting to become obsolete and many are looking for a solution to the problems of credit cards. Since the dawn of the Internet, the idea of ​​creating a digital currency has been brewing. But only recently has this dream come true. It's only been 6 years since the release of the first cryptocurrency, Bitcoin,