laconicd/docs/spec/transactions
2018-08-20 08:33:08 -04:00
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README.md Add transaction doc/spec 2018-08-20 08:33:08 -04:00

Transactions

NOTE: The specification documented below is still highly active in development and subject to change.

Routing

Ethermint needs to parse and handle transactions routed for both the EVM and for the Cosmos hub. We attempt to achieve this by mimicking Geth's Transaction structure and utilizing the Payload as the potential encoding of a Cosmos-routed transaction. What designates this encoding, and ultimately routing, is the Transaction.Recipient address -- if this address matches some global unique predefined and configured address, we regard it as a transaction meant for Cosmos, otherwise, the transaction is a pure Ethereum transaction and will be executed in the EVM.

For Cosmos routed transactions, the Transaction.Payload will contain an embedded encoded type: EmbeddedTx. This structure is analogous to the Cosmos SDK sdk.StdTx. If a client wishes to send an EmbeddedTx, it must first encode the embedded transaction, and then encode the embedding Transaction.

Note: The Transaction and EmbeddedTx types utilize the Amino object serialization protocol and as such, the Transaction is not an exact replica of what will be found in Ethereum. Our goal is to utilize Geth as a library, at least as much as possible, so it should be expected that these types and the operations you may perform on them will keep in line with Ethereum.

Being that Ethermint implements the ABCI application interface, as transactions are sent they are passed through a series of handlers. Once such handler, runTx, is responsible for invoking the TxDecoder which performs the business logic of properly deserializing raw transaction bytes into either an Ethereum transaction or a Cosmos transaction.

Transactions & Messages

The SDK distinguishes between transactions (sdk.Tx) and messages (sdk.Msg). A sdk.Tx is a list of sdk.Msgs wrapped with authentication and fee data. Users can create messages containing arbitrary information by implementing the sdk.Msg interface.

In Ethermint, the Transaction type implements the Cosmos SDK sdk.Tx interface. It addition, it implements the Cosmos SDK sdk.Msg interface for the sole purpose of being to perform basic validation checks in the BaseApp. It, however, has no distinction between transactions and messages.

The EmbeddedTx, being analogous to the Cosmos SDK sdk.StdTx, implements the Cosmos SDK sdk.Tx interface.

Signatures

Ethermint supports EIP-155 signatures. However, just as in Cosmos, Ethermint will support multiple signers. A client is expected to sign the Transaction just as in Ethereum, however, the EmbeddedTx contains a canonical signature structure that itself contains the signature and other information such as an account's sequence number. The sequence number is expected to increment every time a message is signed by a given account. This prevents "replay attacks", where the same message could be executed over and over again.

An EmbeddedTx list of signatures must much the unique list of addresses returned by each message's GetSigners call. In addition, the address of first signer of the EmbeddedTx is responsible for paying the fees and must also match the address of the signer of the embedding Transaction. As such, there will be one duplicate signature.

Gas & Fees

TODO