Mining algorithms

Switching mining algorithms and related issues.

In this section, we discuss mining algorithms. In particular, switching mining algorithms. In both Ethereum and Ethereum Classic, there have been various proposals to change the currently used mining algorithm, ethash, to something else. We first discuss some of the proposals, and then discuss some general issues in switching algorithms.

Switching algorithms

Many proposals have been made to switch the currently used mining algorithms.

Tweaking Ethash

Those set of proposals focus on doing small tweaks on Ethash, but still maintain most of the original algorithm design.

For ASIC resistance

Proposals: EIP-1355, EIP-1485

Ethash was originally designed to be ASIC resistant. However, it’s currently known that Ethash ASICs have been made. As a result, proposals to do slight tweaks on Ethash, to obsolete current ASICs, have been made. Those proposals usually only change a small part of the current specifications, thus can claim to be low risk.

However, criticism says that current ASICs can easily adopt those new algorithm changes.

For hardware inclusion

Proposals of this kind limit the DAG size. Originally, DAG size growth is to provide ASIC resistance. However, it’s currently growing over the range where many commonly used GPUs will not be able to mine.

ProgPoW

Proposals: EIP-1057

ProgPoW is an overhaul of Ethash that aims at providing better utilization of GPUs, and as a result, keeps the original promise of being ASIC resistant.

Keccak256

Another group of people think ASIC resistance is impossible, and maybe even harmful to accomplish. Some proposals attempt to switch to an ASIC friendly algorithm Keccak256.

Difficulty bomb

Proposals: EIP-649, EIP-1234

Difficulty bomb is a mechanic added as the first hard fork on Ethereum, aiming at removing "not doing anything" as the default choice for hard fork.

Ethereum Classic has delayed the difficulty bomb once, and finally ended up removing it. Ethereum has delayed the difficulty bomb twice, and is still counting today.

Issues in signaling

Switching mining algorithms is usually a controversial topic. As a result, some form of signaling is required. The most commonly adopted method is miner vote — allow miners to vote on the change, with one hash, one vote. The issue with this design, however, is that it gives the unchanged algorithm an disproportional advantage — all votes are casted using the unchanged mining algorithm, while we are deciding to switch to a new mining algorithm!

Methods to fix this issue includes:

Doing a soft fork to make the coin dual mining, and gradually decrease the original algorithm’s difficulty.
Use other methods of voting, such as carbon vote, or do not do any form of signaling at all.

Issues in difficulty adjustment

Difficulty of different mining algorithms are not comparable, because the time to calculate one hash of different algorithms in commodity hardware is different. As a result, when switching mining algorithms, major difficulty surge or spike is expected. Developers must be aware of this issue — either design the difficulty adjustment so that it adopts fast and unstable period is short, or preset a new difficulty when the new mining algorithm kicks in.