# eip-4844

https://eips.ethereum.org/EIPS/eip-4844

https://www.eip4844.com/

## Parameters

- `BLOB_TX_TYPE`: 0x03
- `BYTES_PER_FIELD_ELEMENT`: 32 2^5
- `FIELD_ELEMENTS_PER_BLOB`: 4096 2^12

there 2^17 bytes per blob, 131071 bytes

- `BLS_MODULUS`: 52435875175126190479447740508185965837690552500527637822603658699938581184513

order of BLS12-381's \mathbb{G_1} and \mathbb{G_2}

- `VERSIONED_HASH_VERSION_KZG`: 0x01
- `POINT_EVALUATION_PRECOMPILE_ADDRESS`: 0x0A

BLS12-381 的验证 pair 的预编译合约地址

- `POINT_EVALUATION_PRECOMPILE_GAS`: 50000
- `MAX_BLOB_GAS_PER_BLOCK`: 786432
- `TARGET_BLOB_GAS_PER_BLOCK`: 393216 = 786432/2
- `MIN_BLOB_GASPRICE`: 1
- `BLOB_GASPRICE_UPDATE_FRACTION`: 分母，计算预估 gas 的
- `GAS_PER_BLOB`: 2^17
- `HASH_OPCODE_BYTE`: 0x49，blobhash 调用的操纵码
- `HASH_OPCODE_GAS`: 3
- `MIN_EPOCHS_FOR_BLOB_SIDECARS_REQUESTS`: 4096

## Types aliases

- `Blob`: [u8; 2^17]
- `VersionedHash`: Bytes32
- `KZGCommitment`: Bytes48
- `KZGProof`: Bytes48

## Cryptographic Helpers

def kzg_to_versioned_hash(commitment: KZGCommitment) -> VersionedHash:
    return VERSIONED_HASH_VERSION_KZG + sha256(commitment)[1:]

## Blob transaction

[chain_id, nonce, max_priority_fee_per_gas, max_fee_per_gas, gas_limit, to, value, data, access_list, max_fee_per_blob_gas, blob_versioned_hashes, y_parity, r, s]

`to` can't be `nil`

- `max_fee_per_blob_gas`: u256
- `blob_versioned_hashes`: vec[kzg_to_versioned_hash]

## signature

keccak256(BLOB_TX_TYPE || rlp([chain_id, nonce, max_priority_fee_per_gas, max_fee_per_gas, gas_limit, to, value, data, access_list, max_fee_per_blob_gas, blob_versioned_hashes])).

## Block Header
- `blob_gas_used`
- `excess_blob_gas`

## Gas accounting

def calc_data_fee(header: Header, tx: Transaction) -> int:
    return get_total_blob_gas(tx) * get_blob_gasprice(header)

def get_total_blob_gas(tx: Transaction) -> int:
    return GAS_PER_BLOB * len(tx.blob_versioned_hashes)

# MIN_BLOB_GASPRICE * e ** (excess_blob_gas / BLOB_GASPRICE_UPDATE_FRACTION)
def get_blob_gasprice(header: Header) -> int:
    return fake_exponential(
        MIN_BLOB_GASPRICE,
        header.excess_blob_gas,
        BLOB_GASPRICE_UPDATE_FRACTION
    )

## Opcode to get versioned hashes

- `BLOBHASH` 的 opcode 是: HASH_OPCODE_BYTE

输入index，返回 tx.blob_versioned_hashes[index]，超出返回 全0

# Point evaluation precompile

def point_evaluation_precompile(input: Bytes) -> Bytes:
    """
    Verify p(z) = y given commitment that corresponds to the polynomial p(x) and a KZG proof.
    Also verify that the provided commitment matches the provided versioned_hash.
    """
    # The data is encoded as follows: versioned_hash | z | y | commitment | proof | with z and y being padded 32 byte big endian values
    assert len(input) == 192
    versioned_hash = input[:32]
    z = input[32:64]
    y = input[64:96]
    commitment = input[96:144]
    proof = input[144:192]

    # Verify commitment matches versioned_hash
    assert kzg_to_versioned_hash(commitment) == versioned_hash

    # Verify KZG proof with z and y in big endian format
    assert verify_kzg_proof(commitment, z, y, proof)

    # Return FIELD_ELEMENTS_PER_BLOB and BLS_MODULUS as padded 32 byte big endian values
    return Bytes(U256(FIELD_ELEMENTS_PER_BLOB).to_be_bytes32() + U256(BLS_MODULUS).to_be_bytes32())

##