Blockchains use cryptography extensively to secure their data. Cryptographic hash functions are of great importance in this context. Hashing is the process in which a hash function receives an input of any size and returns a hash output of a fixed length. In the hashing process, the output changes with the slightest change in the input. However, if the input is constant, the output will be the same no matter how many times the function is executed.
In the blockchain space, the outputs of functions (hash) are used as unique identifiers in the data block. The hash of each block is created using the hash of the previous block. This creates a chain of blocks. Therefore, the hash of each block depends on the hash of the previous block and the data stored in the block. Hash identifiers play an important role in maintaining the security and immutability of the blockchain.
Cryptoeconomics
Cryptoeconomics is the study of economics in blockchain protocols and the outcome of its design based on the behavior of network users. The security of economics in the crypto space is that the blockchain creates more economic incentives for nodes to act honestly than for malicious behavior. Bitcoin's proof-of-work consensus algorithm is the best example in this area. A user who acts honestly receives a reward from the Bitcoin network. However, if this user behaves maliciously, his computing power and electricity consumption are wasted.
This can ensure the security of the blockchain against possible attacks aimed at controlling the network consensus. The fiercely competitive environment that exists in Bitcoin is such that it is rare for someone or a group to carry out a 51% attack. At the same time, the cost of providing the necessary tools to have 51% consensus power is also very high. Therefore, doing so will not be economically viable in general.

What is scalability in blockchain?
Scalability is the ability of a cryptocurrency to cope with the influx of a large number of transactions at once. For example, Bitcoin has the ability to process seven transactions per second. If there are more than seven transactions per second, all transactions must be placed in a queue to be processed. This queue is formed due to Bitcoin's free fees, which means that if someone pays a higher fee in the meantime, they will have a higher position in this queue. Such an undesirable situation arises due to the limitations of the blockchain. The important point here is that the maximum information that each block can hold is specified in a restrictive way for that block. Such limitations help the system to cope with DDoS attacks on the network more easily. The information that is on the blocks confirming the transfers is the same transactions.
A large number of transactions requires multiple blocks. Miners help a lot in this task. They perform the process of decrypting the blocks along with confirming the transactions. It seems like everyone should be happy with this, but that's not the case. Even with the activity of miners, commissions, etc., cryptocurrencies cannot confirm a large number of transactions at the same time, meaning that in the event of a large influx of transactions, the systems will not be able to cope with this traffic. In this case, the cryptocurrency will experience a temporary shutdown or complete cancellation of the trading queue. Such an event will greatly damage the credibility of the cryptocurrency and, as a result, its price. The scalability problem in blockchain greatly slows down the growth of cryptocurrency technology. For example, due to possible delays and other problems associated with scalability, accepting cryptocurrency payments in restaurants and stores is practically useless. Therefore, all those who specialize in the field of cryptocurrencies and blockchain are looking for a solution to solve the scalability problem in blockchain.