This vulnerability cannot be fixed without adding centralization, claimed Litecoin founder Charlie Lee and Bitcoin Core developer Gregory Maxwell. Decentralization is one of the most important attributes of blockchain technology.

How is the double-spend problem solved? With cash, this problem is trivial. Paper money cannot be in two places at once. But if money is visible only digitally, what prevents people from counterfeiting bills? As the increase in online piracy indicates, duplicating electronic data is simple and hard to control.

Historically, electronic cash was overseen by trusted third parties. Money held in a PayPal account is an example of digital cash managed by a company while the electronic balance in a bank is an example of its management by a government.

How does Bitcoin tackle this problem?

Bitcoin solves the double-spend problem by considering the first transaction as valid.  Any subsequent attempts to spend the same coin are considered invalid. This is where a problem may arise though. The first transaction is defined based on who it is displayed to first. However, if it is displayed twice at the same time, how to decide which is first and which is second?

Bitcoin has solved this problem by voting. Not by people though, because that would require a centralized party to verify their identity and determine who is eligible to vote, and this is not possible within decentralization. Instead, voting takes place by computing power, which does not require the help of a centralized party. Similarly, other sources, for example coins (proof-of-stake) can also be used to count the votes.

Although these measures ensure that attacks are costlier and more complicated, their possibility cannot be eliminated without introducing centralization, said Maxwell.