How does eth_sendTransaction method of ETH JSON-RPC API work

json-rpcsignature

As I understand, this method sends a transaction to the network. But in order for nodes to verify this transaction, the transaction needs to be signed right?

No where in the parameters of this method call does it indicate a signature of the transaction. The only parameters are from, to, gas, etc. How will nodes be able to verify this transaction?

On a related note, the eth_signTransaction method takes in just a transaction object, and returns the signed object. But in order to sign, a node must have the private key of the corresponding public key. Obviously, we cannot just give our private key to any random node in the network, so how does this method return the signed object?

I think I am missing something here with regard to digital signatures and private keys.

Best Answer

For eth_sendTransaction to work the client receiving the transaction should have the private key for sender address.

It is a combination of eth_signTransaction and eth_sendRawTransaction.

Related Solutions

[Ethereum] Dethestify Transaction signing process

This is basically correct. In (4), any node can receive a transaction, check the signature and relay it to other nodes.

The public key can be recovered from the signature, so it doesn't need to be passed around or looked up from anywhere. (This is different from Bitcoin, which wastes bandwidth by passing public keys around in spending transactions; Satoshi doesn't seem to have been that deep into cryptography.)

[Ethereum] How to get signature parameters from a transaction

In the transaction object returned by eth_getTransaction to my geth instance does include the ECDSA parameters:

curl -X POST --data '{"jsonrpc":"2.0","method":"eth_getTransactionByHash","params": ["0x47ced780ecca7c273243dded62c6a240f3ba4332ab067345909a304d7294cfda"],"id":1}' localhost:8545

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "blockHash": "0x7126318b5736f655049fcb7c3f6ef02d0986a5553cb1b1fbc0ca188543b1e60a",
    "blockNumber": "0x339d04",
    "from": "0xea674fdde714fd979de3edf0f56aa9716b898ec8",
    "gas": "0x15f90",
    "gasPrice": "0x4a817c800",
    "hash": "0x47ced780ecca7c273243dded62c6a240f3ba4332ab067345909a304d7294cfda",
    "input": "0x",
    "nonce": "0x15dcf8",
    "to": "0xf34a762291e2578b79646cbf296abf4f5a242b3d",
    "transactionIndex": "0x0",
    "value": "0x16978c7c04171dc",
    "v": "0x26",
    "r": "0xe448b291661c63d8add23a8be2eb726e92ace5c100e902ee75a6396f8df8d221",
    "s": "0x197fb2e88dc2d4e8f606faf6abdb8012d21b024939756ceaf2d39b4bef619fa4"
  }
}

Note the v, r, and s parameters: these are what you need to verify the signature. I'm not sure why these aren't in the official RPC spec, but they are available if you need them

Best Answer

Related Solutions

[Ethereum] Dethestify Transaction signing process

[Ethereum] How to get signature parameters from a transaction

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