Jean-Paul Delahayer is Professor Emeritus at the University of Lille, an expert in theoretical computer science and complexity of algorithms. He just wrote Beyond Bitcoin. In the World of Blockchain and Cryptocurrencies (Dunod, 270 pages, €19.90), an educational book, but also about the strengths and weaknesses of cryptocurrencies, as well as their future.
Why is a mathematician like you interested in cryptocurrencies?
In 2008, Satoshi Nakamoto, whose name is still unknown, proposed the Bitcoin protocol, which creates a currency independent of any central authority, whose activities are based on collective control, all of which is reliable and secure. The key idea lies in the blockchain, a kind of ledger that records transactions without the possibility of erasing pages, which is used throughout the network. This is a brilliant invention. Before him, others tried to develop electronic currencies, but without success. What is new and revolutionary is the development of a protocol that combines already known features, but in an unexpected way that no one could even dream of.
This protocol has also benefited from several improvements launched in 2009. The encryption required to work was quite mature, as evidenced by the success of online banking transactions. Similarly, peer-to-peer or distributed networks have been running without problems for several years. Finally, since the system is based on sharing a large file of about 500 GB, the computers had to have enough memory and processing power.
However, you foresee the failure of Bitcoin, which you describe as a “diplodocus”, a “minitel of cryptocurrencies”, which will be “kept in a computer museum”. Why ?
The main problem with the protocol is how validators are assigned for new transaction pages to be recorded on the blockchain. In the case of bitcoin, the chosen validator is the one who wins the calculation contest, the equivalent of proposing some kind of increasingly valid sudoku grid, or laying down six times six with six dice… In practice, the calculation is hardwired to a cryptographic problem. The consequence of this is competition that is increasingly fierce and more and more expensive in terms of energy. Initially, energy consumption was low, then it increased by about ten times every year and was estimated to be the equivalent of the annual consumption of Switzerland or Sweden, on the order of 100 terawatt-hours! But this is a waste of money because we can do without this type of method. That’s why I’m talking about a bug, a bug for Bitcoin that could have been better designed from the start.
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