EIPs/EIPS/eip-2718.md

eip	title	author	discussions-to	status	type	category	created	requires
2718	Typed Transaction Envelope	Micah Zoltu (@MicahZoltu)	https://ethereum-magicians.org/t/eip-2718-typed-transaction-envelope/4355	Draft	Standards Track	Core	2020-06-13	155

Simple Summary

Defines a new transaction type that is an envelope for future transaction types.

Abstract

TransactionType || TransactionPayload will become a valid transaction and TransactionType || TransactionPayload will become a valid transaction receipt identifying the format of the transaction and *Payload is the transaction/receipt contents, which are defined in future EIPs.

The first two new transaction types will be a wrapped legacy transactions with the formats:

• 0x00 || yParity || r || s || 0x65000000 || rlp(nonce, gasPrice, gasLimit, to, value, data)
• 0x01 || yParity || r || s || 0x65000000 || rlp(nonce, gasPrice, gasLimit, to, value, data, chainId, 0, 0)

The first new receipt will be a wrapped legacy receipt with the format 0 || ssz(status, cumulativeGasUsed, logsBloom, logs).

Motivation

In the past, when we have wanted to add new transaction types we have had to ensure they were backward compatible with all other transactions, meaning that you could differentiate them based only on the encoded payload, and it was not possible to have a transaction that matched both types. This was seen in EIP-155 where the new value was bit-packed into one of the encoded fields. There are multiple proposals in discussion that define new transaction types such as one that allows EOA accounts to execute code directly within their context, one that enables someone besides msg.sender to pay for gas, and proposals related to layer 0 multi-sig transactions. These all need to be defined in a way that is mutually compatible, which quickly becomes burdensome to EIP authors and to clients who now have to follow complex rules for differentiating transaction type.

By introducing an envolope transaction type, we only need to ensure backward compatibility with existing transactions and from then on we just need to solve the much simpler problem of ensuring there is no numbering conflict between TransactionTypes.

Specification

Definitions

• || is the byte/byte-array concatenation operator.
• yParity is the parity (0 for even, 1 for odd) of the y value of the curve point for which r is the x value in the secp256k1 signing process.

Transactions

As of FORK_BLOCK_NUMBER, rlp([nonce, gasPrice, gasLimit, to, value, data, v, r, s]) (legacy transaction) will no longer be a valid Ethereum transaction over the devp2p protocol or in a block.

As of FORK_BLOCK_NUMBER, all transactions sent over devp2p MUST be of the form TransactionType || TransactionPayload where TransactionType is a positive unsigned number between 0 and 0x7f that represents the type of the transcation and TransactionPayload is an opaque byte array whose interpretation is dependent on the TransactionType. New TransactionTypes SHOULD include the TransactionType as the first byte in any signatures they include to minimize the chance of unintentional replay attacks between different transaction types. The transaction hash of all transactions MUST be keccak256(TransactionType || TransactionPayload)

As of FORK_BLOCK_NUMBER, the transaction root in the block header MUST be the root hash of patriciaTrie(transactionIndexInBlock => TransactionType || TransactionPayload) where transactionIndexInBlock is encoded as a big endian 16-bit number.

As of FORK_BLOCK_NUMBER, 0x00 || yParity || r || s || 0x65000000 || rlp(nonce, gasPrice, gasLimit, to, value, data) will be a valid transaction where the RLP encoded transaction portion is signed/processed/handled exactly the same as legacy transactions were signed/processed/handled, with the exception of the final encoding.

As of FORK_BLOCK_NUMBER, 0x01 || yParity || r || s || 0x65000000 || rlp(nonce, gasPrice, gasLimit, to, value, data, chainId, 0, 0) will be a valid transaction where the RLP encoded transaction portion is signed/processed/handled exactly the same as legacy transactions were signed/processed/handled, with the exception of the final encoding.

Receipts

As of FORK_BLOCK_NUMBER, rlp([status, cumulativeGasUsed, logsBloom, logs]) (legacy receipt) will no longer be a valid Ethereum transaction receipt over the devp2p protocol or as part of a block.

As of FORK_BLOCK_NUMBER, all receipts sent over devp2p MUST be of the form TransactionType || ReceiptPayload where TransactionType is a number between 0 and 0x7f that represents the type of the transaction and ReceiptPayload is an opaque byte array whose interpretation is dependent on the TransactionType.

As of FORK_BLOCK_NUMBER, the receipt root in the block header MUST be the root hash of patriciaTrie(transactionIndexInBlock => TransactionType || ReceiptPayload) where transactionIndexInBlock is encoded as a big endian 16-bit number.

As of FORK_BLOCK_NUMBER, 0 || ssz(status, cumulativeGasUsed, logsBloom, logs) will be a valid receipt where the ReceiptPayload will be generated/processed/handled exactly the same as legacy receipts were processed/handled with the exception of its encoding.

As of FORK_BLOCK_NUMBER, 1 || ssz(status, cumulativeGasUsed, logsBloom, logs) will be a valid receipt where the ReceiptPayload will be generated/processed/handled exactly the same as legacy receipts were processed/handled with the exception of its encoding.

Fork Block Transition

Between FORK_BLOCK_NUMBER - 1 and FORK_BLOCK_NUMBER clients SHOULD convert all transactions in their local pending pool into type 0 transactions. Clients MAY choose to flush their pending pool instead, if it is not possible to do the wrapping in time for the next block, though this is discouraged.

As of FORK_BLOCK_NUMBER, clients SHOULD accept incoming transactions over user/application facing APIs such as JSON-RPC in both the new wrapped format and the legacy format. If a legacy format transaction is received, the client MUST wrap it in a type 0 envelope before sending it over devp2p or including it in a block.

As of FORK_BLOCK_NUMBER, clients SHOULD return type 0 receipts over user/application facing APIs such as JSON-RPC in the legacy format. Clients SHOULD devise a long term strategy for deprecating the legacy format over APIs in favor of the typed receipt envelope format.

Rationale

Not including the type in type 6 signatures

While this EIP recommends that the envelope be included in any signatures, it also specifies that for Transaction Type 0 the envelope is not included in the signature. This EIP disobayes its own recommendation because we don't want all signing tools to break on the fork block and require updates to start working again.

TransactionType only goes up to 0x7f

For the forseable future, 0x7f is plenty and it leaves open a number of options for extending the range such as using the high bit as a continuation bit. This also prevents us from colliding with legacy transaction types, which always start with a byte >= 0xc0.

TransactionType selection algorithm

There was discussion about defining the TransactionType identifier assignment/selection algorithm in this standard. While it would be nice to have a standardized mechanism for assignment, at the time of writing of this standard there is not a strong need for it so it was deemed out of scope. A future EIP may introduce a standard for TransactionType identifier assignment if it is deemed necessary.

Opaque byte array rather than an RLP array

By having the second byte on be opaque bytes, rather than an RLP (or other encoding) list, we can support different encoding formats for the transaction payload in the future such as SSZ, LEB128, or a fixed width format.

ORIGIN and CALLER

There was discussion about having ORIGIN and CALLER opcodes be dependent on the transaction type, so that each transaction type could define what those opcodes returned. However, there is a desire to make transaction type opaque to the contracts to discourage contracts treating different different types of transactions differently and there also were concerns over backward compatibility with existing contracts which make assumptions about ORIGIN and CALLER opcodes. Going forward, we will assume that all transaction types will have an address that reasonably represents a CALLER of the first EVM frame and ORIGIN will be the same address in all cases. If a transaction type needs to supply additional information to contracts, they will need a new opcode.

Hashing the outer transaction

If you submit a transaction prior to the fork block and it is mined after the fork block, the transaction hash of the mined transaction will not match the the transaction hash of the transaction you originally submitted. This is because the mined transaction will be a wrapped one, while the submitted transaction will be unwrapped. Applications that use the transaction hash to lookup the transaction result will fail to ever find it or see it ever mined. Clients can optionally choose to track type 6 transactions internally by both hashes for a period of time so that lookups of the old hash won't fail for the user, but this is not required for consensus.

TransactionType 0 & 1 instead of just 0 that matches legacy

Legacy transactions were quite complicated due partially to EIP-155 and partially to the way they are encoded. This change should reduce complexity in clients by making it easier to validate transactions, and it moves the complexities around EIP-155 and transaction encoding out near the JSON-RPC layer.

• Legacy transactions have to be RLP decoded first, the signature extracted, and then RLP encoded without the signature in order to validate them.
• Legacy transactions have to extract and process the v value before they can recreate the signed data for validation.

TransactionType 0/1 0x65000000 element

0x00 || yParity || r || s || 0x65000000 || rlp(nonce, gasPrice, gasLimit, to, value, data) is the same as ssz(0, yParity, r, s, rlp(nonce, gasPrice, gasLimit, to, value, data)), which may prove convenient for some clients. It costs us 4 extra bytes on the wire (mostly zeros), but the authors deem this a worthwhile trade to be SSZ encodable/decodable.

Backwards Compatibility

Clients can differentiate between the legacy transactions and typed transactions by looking at the first byte. If it starts with a value in the range [0, 0x7f] then it is a new transaction type, if it starts with a value in the range [0xc0, 0xff] then it is a legacy transaction type.

Test Cases

TBD

Implementation

TBD

Security Considerations

TBD

Copyright

Copyright and related rights waived via CC0.