BIT-0017: Neuron UID registration

[surcyf123]

Current issues:

• large burn price fluctuations
• long periods where nobody can register

Proposed fixes:

• price changes every block not every interval
• remove all rate limits from registration

[surcyf123]

the price should decrease every block, not only once per half life. Not sure if that was clear.

[ppolewicz]

Suggested change

	Subnets will have a cost that decays as determined by BurnHalfLife and increases by BurnIncreaseMult the block after a registration. MaxRegrationsPerInterval will still be 1.
	Subnets will have a cost that decays as determined by `BurnHalfLife` and increases by `BurnIncreaseMult` the block after a registration. `MaxRegrationsPerBlock` will still be 1.

[RD4Fun]

half life is a exponential reduction similar to halving
I think that the formula a linear reduction in value by block - same as subnet registration
NeuronReductionInterval: Number of blocks until the registration price halves from the current value
NeuronIncreaseMult: registration price Multiplier (default is 2)
formula is:

neuron_burn_price = (burn_at_last_reg * NeuronIncreaseMult) - (burn_at_last_reg / NeuronReductionInterval) * (current_block - last_reg_block)
neuron_burn_price = max (neuron_burn_price, minBurnCost)

[ppolewicz]

the new hyperparameters must be limited in such a way that does not in practice allow the subnet owner to prevent the root validators from getting a neuron

[RD4Fun]

Attack vectors

1. Owner increasing the NeuronReductionInterval so the price remains high for many days (up to 65535 blocks)
   • need to set a high limit to the possible value of NeuronReductionInterval
2. Owner decreasing the NeuronReductionInterval to 1 or 2 to snipe a cheap registration then resetting the interval to a long value
   • the reset to a high value is blocked by the hyperparameter change rate limit
3. Owner increasing the NeuronIncreaseMult above 16 so the price remains high for a very long time
   • make this parameter a sudo call
4. Owner decreasing the NeuronIncreaseMult to less than 1 ... makes it cheap for all miners to be deregistered and forced into immunity
   • make this parameter a sudo call
5. Miner using a script to register

• timing is now longer block based, its price based
• script must pay more for registrations as each registration price increases

6. Miner using MeV tactics to snipe the cheapest registration

• FIFO on the Proof of authority nodes
• the sniping miner must pay more for his registrations as he can no longer batch register at the one price

7. Miner blocking anyone else from registering

• the price doubling each registration makes it economically cost prohibitive

Mitigation - limits and formulas

1. range limit the NeuronIncreaseMult from 1 to 5 with up to 3 decimal points
2. range limit NeuronReductionInterval from 1 to x where x is a small multiple of days

[ppolewicz]

NeuronReductionInterval should be controlled by the owner but throttled to like one change a week and capped in a tight range maybe? It only makes sense to change it when uid pressure changes