Jean-Paul Delahaye is professor emeritus at the University of Lille, specializing in theoretical computer science and the complexity of algorithms. He just wrote Beyond Bitcoin. In the world of blockchain and cryptocurrency (Dunod, 270 pages, 19.90 euros), an educational book, but also committed to the strengths and weaknesses of cryptocurrencies, as well as their future.
Why is a mathematician like you interested in cryptocurrency?
In 2008, Satoshi Nakamoto, whose name is still unknown, proposed a protocol, Bitcoin, to create a currency independent of any central authority, whose functionality is based on collective control, all robust and secure. The basic idea is blockchain, a kind of account book recording transactions without the possibility of erasing pages, which is shared across the network. This is a brilliant invention. Before that, others tried to develop electronic currency, but did not succeed. What is new and revolutionary is the development of a protocol that combines functions that are already known, but in an unexpected and unimagined way.
This protocol has also benefited from several advances since its launch in 2009. Encryption, essential to operations, was quite mature, as shown by the success of banking transactions on the Internet. Similarly, peer-to-peer or distributed networks have been working for several years without problems. Finally, since the system is based on sharing a large file of about 500 GB, the computers must have sufficient memory and computing power.
However, you predicted the failure of Bitcoin, which you described as a “diplodocus”, a “miniature of cryptocurrencies”, which would be “stored in a computer museum”. Why?
The main problem with the protocol is in the way it designates validators for new transaction pages to be recorded on the blockchain. With Bitcoin, the chosen validator is the one who wins a calculation competition equivalent to proposing an increasingly valid sudoku grid, or rolling out six times six with six dice… In reality, the calculation is linked to a cryptographic problem that is difficult. The result is a competition, increasingly difficult and more expensive in energy. Initially, the energy cost was low, then it increased almost tenfold every year to represent, according to estimates, equivalent to the annual consumption of Switzerland or Sweden, on the order of 100 terawatt hours! But this is a useless expense, because we can do without such methods. That’s why I’m talking about a bug, a flaw for Bitcoin, which could have been designed better from the start.
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