Update EIP-7594: include cell proofs in network wrapper of blob txs

EIPS/eip-7594.md

@@ -29,10 +29,39 @@ Nodes find and maintain a diverse peer set and sample columns from their peers t
 
 A node can reconstruct the entire data matrix if it acquires at least 50% of all the columns. If a node has less than 50%, it can request the necessary columns from the peer nodes.
 
-The detailed specifications are on [ethereum/consensus-specs](https://github.com/ethereum/consensus-specs/blob/b4188829b32139916127827c64ba17c923e66c3c/specs/_features/eip7594/das-core.md).
+The detailed specifications are on [ethereum/consensus-specs](https://github.com/ethereum/consensus-specs/tree/9d377fd53d029536e57cfda1a4d2c700c59f86bf/specs/fulu/).
 
 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 and RFC 8174.
 
+### Networking
+
+This EIP introduces cell KZG proofs, which are used to prove that a KZG commitment opens to a cell at the given index. This allows downloading only specific cells from a blob, while still ensuring data integrity with respect to the corresponding KZG commitment, and is therefore a key component of data availability sampling. However, computing the cell proofs for a blob is an expensive operation, which a block producer would have to repeat for many blobs. Since proof verification is much cheaper than proof computation, and the proof size is negligible compared to cell size, we instead require blob transaction senders to compute the proofs themselves and include them in the EIP-4844 transaction pool wrapper for blob transactions.
+
+To this end, during transaction gossip responses (`PooledTransactions`), the wrapper is modified to:
+
+```
+rlp([tx_payload_body, wrapper_version, blobs, commitments, cell_proofs])
+
+cell_proofs = [cell_proof_0, cell_proof_1, ...]
+```
+
+The `tx_payload_body`, `blobs` and `commitments` are as in EIP-4844, while the `proofs` field is replaced by `cell_proofs`, and a `wrapper_version` is added. These are defined as follows:
+
+- `wrapper_version` - one byte indicating which version of the wrapper is used. For the current one, it is set to `1`.
+- `cell_proofs` - list of cell proofs for all `blobs`, including the proofs for the extension indices, for a total of `CELLS_PER_EXT_BLOB` proofs per blob (`CELLS_PER_EXT_BLOB` is the number of cells for an extended blob, defined [in the consensus specs](https://github.com/ethereum/consensus-specs/tree/9d377fd53d029536e57cfda1a4d2c700c59f86bf/specs/fulu/polynomial-commitments-sampling.md#cells)) 
+
+Note that, while `cell_proofs` contain the proofs for all cells, including the extension cells, the blobs themselves are sent without being extended (`CELLS_PER_EXT_BLOB / 2` cells per blob). This is to avoid sending redundant data, which can quickly be computed by the receiving node.
+In other words, `cell_proofs[i * CELLS_PER_EXT_BLOB + j]` is the proof for cell `j` of `compute_cells(blobs[i])`, where `compute_cells(blob)` outputs all cells of `blob`, including the extension cells.
+
+The node MUST validate `tx_payload_body` and verify the wrapped data against it. To do so, ensure that:
+
+- There are an equal number of `tx_payload_body.blob_versioned_hashes`, `blobs` and `commitments`.
+- `cell_proofs` contains exactly `CELLS_PER_EXT_BLOB * len(blobs)` cell proofs
+- The KZG `commitments` hash to the versioned hashes, i.e. `kzg_to_versioned_hash(commitments[i]) == tx_payload_body.blob_versioned_hashes[i]`
+- The KZG `commitments` match the corresponding `blobs` and `cell_proofs`. This requires computing the extension cells for all `blobs`, and verifying all `cell_proofs`. (Note: all cell proofs can be batch verified at once)
+
+
+
 ## Rationale
 
 TBD