The blockchain is also known as a tech ledger on which the Bitcoin network runs smoothly, in other words, experts consider it to be a shared, decentralized and unrestricted ledger. The most basic level description is that blockchain is just an uncomplicated chain of blocks where the digital information is the block and the public database is called the chain. It also grants more refined clarity and traceability for numerous business processes.

How Secure is a Blockchain?

This technology accounts for the obstacles of security and trust in several different ways. First of all, brand new blocks are stored in chronological order, the new ones are always added at the end of the chain of info.

By closely examining Bitcoin’s blockchain system, we can see that every block has a certain place on the chain of information, which is called height and as of February 2020, the block’s height is over 616,494 blocks.

One brilliant hallmark here is that once a block has been added at the end of the chain, it is almost inconceivable to go back and bring alterations to the contents of the block. This situation is a reality because each block contains its information and it is equipped with the hash of the preceding block.

Hash codes are created by math algorithms that transpose into digital information into a very long string of numbers and letters. If someone even gets close to editing that information the hash code immediately changes.

Hacking Techniques

As for security purposes let’s consider that a hacker tries to alter your transaction which will make you pay twice for your acquisition. The clever part is when they begin editing the value of the dollar from the transaction then the block’s hash will instantly adapt to the new setting.

Moreover, the following block in the chain will still retain the old unmodified hash hence forcing the hacker to update that next block and after changing that one the next one and so on, a long line of revisions deemed impossible to implement.

In short, a hacker would need to change every single block one after another and recalculating all the hashes would take a doubtful amount of computing energy and time.

A Blockchain is, in Theory, Hacker-Proof

In theory, a hacker can take advantage of the majority in what is known as a 51% attack. Let’s assume that there are almost four million computers on the entire network and to have the majority, a hacker would require taking control of at least two million and one of these computers. By doing so, a hacker could influence or modify the process of registering new transactions. A hacker could also send a transaction and then reverse it, therefore making it look as if they spent credit.

This vulnerability is known in the branch as double-spending and it is the equivalent of counterfeiting real money, this enables the hacker to spend their coins twice.

An attack of this dimension is almost inconceivable to set into motion because it requires the hacker to take complete control of millions and millions of computers.

For example, this attack would have been possible to occur when Bitcoin was founded in 2009 when there were only a few users, a majority back then would’ve been rather easy to form.

A Closer Analysis of Internal and External Security Characteristics

1) PKI technology hardware wallets

Security issues started to appear more often as many users fear this type of 51% attack which is capable of restraining transactions. Nonetheless, users have other ways of defending their transactions, for example in Blocknomi, an online media company based in Manchester, United Kingdom, a journalist by the name of Nicholas Say wrote that “the needs for new custodial solutions require the usage of non-programmable hardware devices such as PKI technology wallets which have the sole purpose of providing accurate and advanced safety features. This kind of advanced security will allow a person to use their cryptos online with a higher level of confidence than other systems”.

2) Consensus models

To address the problem of trust, blockchain networks have already begun implementing special tests for all computers that wish to connect and to add blocks to the chain. These tests are named consensus models and they are the equivalent of two-step verification.

3) The proof of work

Computers that are present in the system must confirm their identity by solving a very complex computational mathematical problem. If a computer can resolve it, then they become qualified to add a block to the chain.

Concluding reflections

These inventive methods of security do not fully incapacitate a hacker because hackers will always try to find different ways, but in case if a hacker somehow finds success on the blockchain system it will be entirely fruitless because users have supplementary security features at their disposal.
In the end, it comes down to a clear solid idea, if hackers want to convey an attack on the blockchain system itself, they would require to dominate more than 50% of all the computing energy currently present on the system to overcome all other participants in the network. But given the immense volume of the blockchain and its growing popularity, a so-called 51% assault is not even worth the compelling effort and it is more than likely highly unlikely to take place, as some might put it, it is simply absurd.