1. Some argue that mining crypto could be positive for alternative energy producers, enabling them to turn excess energy not required otherwise to be turned into money, therefore leading to faster amortization (or higher return on investment) for the operator. Residential electricity needs peak in the morning and evening, while the sun peaks at noon, so there is a mismatch that cypto mining might be able to alleviate. Also, sun-rich but otherwise poor countries (Sahara) might be able to improve standard of living for their citizens by solar-powered mining.

  2. Any non-reversible computation, like the hash function used by bitcoin, consumes energy. So energy consumption is an inevitable fact of doing bitcoin mining,” says Joseph Bonneau, a postdoctoral researcher at Stanford University.

    What Joseph Bonnaeu is attempting to allude to is the fact that by Landauer’s principle, every bit erased costs k*T*ln(2) energy where k is Boltzmann’s constant (k=1.38*10^(-23) Joules/second), T is the temperature, and ln is the natural logarithm. By irreversible computation, Bonnaeu means a computation that deletes information while a reversible computation is a computation that does not delete any information. Landauer’s limit does not apply to reversible computation, and there are no theoretical limits to the energy efficiency of reversible computation. Bonnaeu however has committed the there-can’t-possibly-be-an-efficient-reversible-algorithm-that-does-so-and-so fallacy where he assumed that there cannot be any efficient completely reversible algorithm that mines Bitcoin.

    1. Cryptocurrency mining problems are quite amenable to reversibility. After all, collision resistance is a weak form of reversibility, and the best way to ensure collision resistance is to incorporate reversible components into your cryptographic hash function.

    2. If you look at the algorithm for SHA-256, you will notice that it contains many instances of modular addition, and modular addition can be computed using reversible ripple carry adders. SHA-256 is therefore quite amenable to reversible computation.

    3. In this paper https://arxiv.org/pdf/math/9508218.pdf, you can see that any computation can be carried out in a completely reversible manner with a quite reasonable computational complexity overhead.

    4. Any cryptocurrency mining problem can be mined reversibly with only a linear space/time overhead.

    5. Before you state that Bitcoin mining cannot be done reversibly, perhaps you should write a program in the reversible programming language Janus so that you know how reversible computation works in practice.

    I always have to correct people about this issue and it is getting really old really quickly.

    On a related note, people still use SHA-256 as a cryptocurrency mining problem while SHA-256 mining has some bugs since it is susceptible to ASIC-BOOST, approximate mining, and it is an algorithm which was not designed for cryptocurrency mining. Instead, people should use a cryptocurrency mining problem which is specifically designed for cryptocurrencies instead of a mining problem with these bugs. I personally have designed such a mining problem myself which is optimized so that it will incentivize the development of the energy efficient reversible computer (in other words, people will build reversible computers in order to efficiently mine this cryptocurrency). Such a mining problem cannot be considered wasteful since the resources will be spent on a good cause.

    I have contacted Bonnaeu’s colleagues about this issue, so there is no excuse.

    -Joseph Van Name Ph.D.

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