Summary

Introduce a protocol-level minimum gas per transaction (min_tx_gas) to enforce a floor on fees (e.g. ~0.005 DUSK, 5M LUX) without globally increasing the gas_price and affecting more computationally expensive transactions (withdraw/stake/unstake). The rationale for this is to combat the too low transaction fees on mainnet.

Possible solution design or implementation

Add min_tx_gas to the VM execution config, activated via a feature flag at a chosen block height. In vm::execute we should reject transactions with gas_limit < min_tx_gas if the feature is active, and for successful calls, floor the receipt.gas_spent to at least the min_tx_gas (capped by gas_limit), and composed with existing blob/deploy charging.

In the mempool preverify we should require gas_limit >= max(min_gas_limit, min_tx_gas) (taking into account min_tx_gas if active, or the existing min_gas_limit if the feature is not active), and return a GasLimitTooLow error if the condition is not met.

Additional context

We currently set a minimum of 0.0025 DUSK (2.5M LUX) in the Rusk wallet, this change will thus require a new release of the Rusk wallet. The web wallet is not affected.