This EIP defines a signature scheme for native Simple Serialize (SSZ) encoded transactions.
EIP-6404 introduces SSZ transactions by converting from RLP transactions. Defining a signature scheme for native SSZ transactions further reduces required conversions and unlocks the forward compatibility benefits of SSZ ProgressiveContainer.
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.
Native SSZ transactions are based on the TransactionPayload defined in EIP-6404 and emit an EIP-6466 Receipt. To distinguish native SSZ transactions from those converted from RLP, native SSZ transactions do not contain the RLP TransactionType field in their TransactionPayload.
All native SSZ transactions follow a scheme based on hash_tree_root to compute their signing hash (sig_hash). Likewise, native SSZ authorizations use such a scheme to derive their signing hash (auth_hash).
Additional information is mixed into sig_hash and auth_hash to uniquely identify the underlying specification and avoid hash collisions across different signature kinds. Vendor-defined networks MUST use a different DomainType for signing custom transaction or authorization types.
| Name | Value | Description |
|---|---|---|
DOMAIN_TX_SSZ | DomainType('0x01000008') | DomainType for signing native SSZ transactions compatible with this EIP |
DOMAIN_AUTH_SSZ | DomainType('0x02000008') | DomainType for signing native SSZ authorizations compatible with this EIP |
New EIP-6404 TransactionPayload definitions are introduced to represent native SSZ transactions:
BasicTransactionPayload and CreateTransactionPayload share the functionality of EIP-1559 fee market transactionsBlobTransactionPayload shares the functionality of EIP-4844 blob transactionsSetCodeTransactionPayload shares the functionality of EIP-7702 set code transactions; native SSZ types are introduced for authorizationsThe helpers from EIP-6404 are updated to support native SSZ transactions.
| Name | Value | Description |
|---|---|---|
SSZ_TX_TYPE | TransactionType(0x1f) | Endpoint specific SSZ object |
Certain JSON-RPC endpoints such as eth_getTransactionByHash indicate the corresponding EIP-2718 envelope type prefix in a type field.
When representing native SSZ transactions on such endpoints, SSZ_TX_TYPE SHOULD be indicated as their type. Omitting the type is NOT RECOMMENDED as certain client applications could confuse the omission with untyped LegacyTransaction.
The unique RPC transaction identifier tx_hash for native SSZ transactions is defined to match the EIP-6404 tx_root value.
The SSZ signature scheme reduces hashing overhead and ensures that tx_hash commitments are available on-chain. It also provides a flexible basis for future transaction functionality.
The new transaction signature scheme is solely used for native SSZ transactions and is representable using a unique EIP-2718 envelope type prefix (SSZ_TX_TYPE) different from existing RLP transactions.
SSZ signatures MUST NOT collide with RLP transaction and message hashes.
As RLP messages are hashed using keccak256, and all SSZ objects are hashed using SHA256. These two hashing algorithms are both considered cryptographically secure and are based on fundamentally different approaches, minimizing the risk of hash collision between those two hashing algorithms.
Furthermore, RLP messages are hashed linearly across their serialization, while SSZ objects are hashed using a recursive Merkle tree. Having a different mechanism further reduces the risk of hash collisions.
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