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ps: this is an iteration over block access list with inputs and refinements from @pipermerriam

Background

EIP 2929/2930 centers around normalizing (low) gas costs of data/storage accesses made by a transaction as well as providing for (and encouraging) a new transaction type format: 0x01 || rlp([chainId, nonce, gasPrice, gasLimit, to, value, data, access_list, yParity, senderR, senderS]), that makes upfront access_list declarations, where access_list is some [[{20 bytes}, [{32 bytes}...]]...] a map of accessed_address => accessed_storage_keys.

The first accesses of these upfront declarations are charged at discounted price (roughly ~10%) and first accesses outside this list are charged higher price. Reason is, upfront access declaration provides for a way to preload/optimize/batch loading these locations while executing the transaction. This inadvertently leads to generation of transaction access_list that has all first accesses (declared or not) made by a transaction. A JSON-RPC api endpoint for creating and fetching this list is being standardized.

Motivation

Motivation is to collate these transaction access_lists for all the transactions in a block_access_list document, that can serve as sort of access index in the block to give following benefits:

  1. Block execution/validation optimizations/parallelization by enabling construction of a partial order for access and hence execution (hint: chains in this poset can be parallelized).
  2. Enabling partial inspection and fetching/serving of a block data/state by light sync or fast sync protocols concerned with a subset of addresses.
  3. Possible future extension of this list to serve as index for bundling, serving and fetching witness data for stateless protocols.

To serve the above purpose, and prevent any grieving attacks, AccessListRoot which could be a urn encoding Hash/Commitment of a canonical construction of block_access_list as well as the construction type (merkel/verkel) will need to be included in the block header. Forming the tree structure (merkel/verkel) rather than a simple hashing/commitment of the entire canonical block_access_list will be a bit more expensive, but it will enable partial downloading, inspection and validation of the block_access_list as well and is recommended.

Construction