Good morning Karl,

> Hi,
> I'd like to revisit the discussion of the digest algorithm used in hashcash.
> I believe migrating to new hashing algorithms as a policy would significantly 
> increase decentralization and hence security.

Why do you believe so?

My understanding is that there are effectively two strategies for ensuring 
decentralization based on hash algorithm:

* Keep changing the hash algorithm to prevent development of ASICs and ensure 
commodity generic computation devices (GPUs) are the only practical target.
* Do not change the algorithm, to ensure that knowledge of how best to 
implement an ASIC for the algorithm becomes spread out (through corporate 
espionage, ASIC reverse-engineering, patent expiry, and sheer engineering 
effort) and ASICs for the algorithm are as commoditized as GPUs.

The former strategy has the following practical disadvantages:

* Developing new hash algorithms is not cheap.
  The changes to the hashcash algorithm may need to occur faster than the speed 
at which we can practically develop new, cryptographically-secure hash 
* It requires coordinated hardforks over the entire network at an alarmingly 
high rate.
* It arguably puts too much power to the developers of the code.

On the other hand, the latter strategy requires us only to survive an 
intermediate period where ASICs are developed, but not yet commoditized; and 
during this intermediate period, the centralization pressure of ASICs might not 
be more powerful than other centralization pressures


Which brings us to another point.

Non-ASIC-resistance is, by my understanding, a non-issue.

Regardless of whether the most efficient available computing substrate for the 
hashcash algorithm is CPU, GPU, or ASIC, ultimately miner earnings are 
determined by cost of power supply.

Even if you imagine that changing the hashcash algorithm would make CPUs 
practical again, you will still not run it on the CPU of a mobile, because a 
mobile runs on battery, and charging a battery takes more power than what you 
can extract from the battery afterwards, because thermodynamics.

Similarly, geographic locations with significant costs of electrical power will 
still not be practical places to start a mine, regardless if the mine is 
composed of commodity server racks, commodity video cards, or commodity ASICs.

If you want to solve the issue of miner centralization, the real solution is 
improving the efficiency of energy transfer to increase the areas where cheap 
energy is available, not stopgap change-the-algorithm-every-6-months.


> I believe the impact on existing miners could be made pleasant by gradually 
> moving the block reward from the previous hash to the next (such that both 
> are accepted with different rewards).  An appropriate rate could possibly be 
> calculated from the difficulty.
> You could develop the frequency of introduction of new hashes such that once 
> present-day ASICs are effectively obsolete anyway due to competition, new 
> ones do not have time to develop.
> I'm interested in hearing thoughts and concerns.
> Karl Semich

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