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Little Guide of eth_wallet

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李大狗
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Little Guide of eth_wallet

0x00 Preface

Remember to Link Runtime to eth_wallet!

0x01 Generate Keys

Step 0x01. Generate Keys(Priv and Pub) by secp256k1:

 {pubkey, privkey} = :crypto.generate_key(:ecdh, :secp256k1)
 {pubkey, privkey} = :crypto.generate_key(:ecdh, :secp256k1, privkey)

Step 0x02 Pubkey to Addr:

  @address_size 40
  
  defp pubkey_to_hex(public_key) do
    public_key
    |> strip_leading_byte()
    |> keccak_256sum()
    |> String.slice(@address_size * -1, @address_size)
    |> String.downcase()
  end
 defp keccak_256sum(data) do
    data
    |> kec()
    |> Base.encode16()
  end

  def kec(data) do
    ExSha3.keccak_256(data)
  end
EthWallet.generate_keys()
%{
  addr: "0x47ec2193b73b8b003645760df71569ae5e4b810c",
  priv: <<179, 57, 147, 246, 138, 161, 157, 91, 107, 216, 233, 48, 101, 29, 134, 144, 159, 60, 19,
    74, 2, 54, 0, 229, 207, 243, 60, 124, 244, 9, 123, 148>>,
  pub: <<4, 55, 136, 222, 230, 58, 251, 181, 80, 218, 32, 32, 98, 161, 105, 198, 228, 22, 123, 211,
    63, 23, 172, 130, 39, 34, 184, 155, 75, 92, 229, 101, 100, 82, 150, 187, 138, 22, 109, 147, 26,
    200, 28, 243, 6, 4, 137, ...>>
}

0x02 Encrypt Keys for Database Saving

priv =
  <<179, 57, 147, 246, 138, 161, 157, 91, 107, 216, 233, 48, 101, 29, 134, 144, 159, 60, 19, 74,
    2, 54, 0, 229, 207, 243, 60, 124, 244, 9, 123, 148>>

EthWallet.encrypt_key(priv, "abcdefg")
<<48, 139, 144, 30, 52, 58, 66, 201, 227, 43, 238, 134, 90, 103, 233, 249, 233, 34, 36, 16, 68, 254,
  183, 4, 127, 47, 84, 195, 99, 114, 31, 160, 221, 56, 52, 255, 75, 164, 192, 239, 129, 61, 220,
  205, 161, 163, 172, 29, 94, 17, ...>>

0x03 Build Transaction

Struct of Transaction:

  @type t :: %__MODULE__{
          nonce: integer(),
          gas_price: integer(),
          gas_limit: integer(),
          to: <<_::160>> | <<_::0>>,
          value: integer(),
          # contract machine code
          init: binary(),
          data: binary(),

          # signature
          v: integer(),
          r: integer(),
          s: integer(),
        }

Func to transfer addr to bin:

  @spec addr_to_bin(String.t()) :: binary()
  def addr_to_bin(addr_str) do
    addr_str
    |> String.replace("0x", "")
    |> Base.decode16!(case: :mixed)
  end

Example:

gas_price = 20_000_000_000
gas_limit = 300_000
EthWallet.build_tx("0x47ec2193b73b8b003645760df71569ae5e4b810c", 1, <<>>, 3, gas_price, gas_limit)
%EthWallet.Transaction{
  data: "",
  gas_limit: 300000,
  gas_price: 20000000000,
  init: "",
  nonce: 3,
  r: nil,
  s: nil,
  to: <<71, 236, 33, 147, 183, 59, 139, 0, 54, 69, 118, 13, 247, 21, 105, 174, 94, 75, 129, 12>>,
  v: nil,
  value: 1
}

Knowledge about gas

  • Ether (ETH) is the Ethereum network’s native cryptocurrency, the second-largest by market cap on the crypto market.

  • Gas is the unit of calculation that indicates the fee for a particular action or transaction.

  • The Gas Limit is the maximum amount of Gas that a user is willing to pay for performing this action or confirming a transaction (a minimum of 21,000).

  • The price of Gas (Gas Price) is the amount of Gwei that the user is willing to spend on each unit of Gas.

1 ether = 1 x 10^18 wei = 1 x 10^9 Gwei

U can check the gas fee by Etherscan or the Blocknative Chrome Plugin.

Knowledge about data

if you only transfer ether, data is empty; but it’s necessary if you send transaction to a contract or deploy a contract.

Knowledge about Nonce

A scalar value equal to the number of transactions sent from this address or, in the case of accounts with associated code, the number of contract-creations made by this account.

# Nonce begin from zero, so tx_count = nonce
@spec get_nonce(String.t()) :: integer
def get_nonce(addr) do
  # HttpClient is a module in Ethereumex
  {:ok, hex} = HttpClient.eth_get_transaction_count(addr)
  TypeTranslator.hex_to_int(hex)
end

You can check the api here:

https://infura.io/docs/ethereum/json-rpc/eth-getTransactionCount

REQUEST PARAMS

  • ADDRESS [required] - a string representing the address (20 bytes) to check for transaction count for
  • BLOCK PARAMETER [required] - an integer block number, or the string “latest”, “earliest” or “pending”, see the default block parameter 
curl https://mainnet.infura.io/v3/YOUR-PROJECT-ID \
    -X POST \
    -H "Content-Type: application/json" \
    -d '{"jsonrpc":"2.0","method":"eth_getTransactionCount","params": ["0xc94770007dda54cF92009BFF0dE90c06F603a09f","0x5bad55"],"id":1}'

0x04 Sign Transaction

sign transaction by transaction generate above and privkey:

  @spec sign_tx(Transaction.t(), binary(), integer() | nil) :: Transaction.t()
  def sign_tx(tx, private_key, chain_id \\ nil) do
    %{v: v, r: r, s: s} =
      tx
      |> hash_for_signing(chain_id)
      |> Crypto.sign_compact(private_key, chain_id)

    %{tx | v: v, r: r, s: s}
  end

  @spec hash_for_signing(Transaction.t(), integer() | nil) :: binary()
  def hash_for_signing(tx, chain_id \\ nil) do
    # See EIP-155
    tx
    |> serialize(false)
    |> Kernel.++(if chain_id, do: [:binary.encode_unsigned(chain_id), <<>>, <<>>], else: [])
    |> ExRLP.encode(encoding: :binary)
    |> Crypto.kec()
  end

Finally get r, s, v.

The explaination a bout signature and r, s, v:

https://ethfans.org/posts/the-magic-of-digital-signatures-on-ethereum 

priv =
  <<179, 57, 147, 246, 138, 161, 157, 91, 107, 216, 233, 48, 101, 29, 134, 144, 159, 60, 19, 74,
    2, 54, 0, 229, 207, 243, 60, 124, 244, 9, 123, 148>>

gas_price = 20_000_000_000
gas_limit = 300_000

tx =
  EthWallet.build_tx(
    "0x47ec2193b73b8b003645760df71569ae5e4b810c",
    1,
    <<>>,
    3,
    gas_price,
    gas_limit
  )

EthWallet.sign_tx(tx, priv)
%EthWallet.Transaction{
  data: "",
  gas_limit: 300000,
  gas_price: 20000000000,
  init: "",
  nonce: 3,
  r: 67243437211985125846499025668706844111533160274980950914994922050681896081880,
  s: 56427494744604503742191182187154037327356481500982047507792388036469495366909,
  to: <<71, 236, 33, 147, 183, 59, 139, 0, 54, 69, 118, 13, 247, 21, 105, 174, 94, 75, 129, 12>>,
  v: 27,
  value: 1
}

0x05 Get Raw Transaction

Signed Tx to Raw:

  @spec signed_tx_to_raw_tx(Transaction.t()) :: String.t()
  def signed_tx_to_raw_tx(signed_tx) do
    raw_tx =
      signed_tx
      |> serialize()
      |> ExRLP.encode(encoding: :hex)

    "0x" <> raw_tx
  end

Serialize:

 @spec serialize(Transaction.t(), boolean()) :: ExRLP.t()
  def serialize(tx, include_vrs \\ true) do
    base = [
      encode_unsigned(tx.nonce),
      encode_unsigned(tx.gas_price),
      encode_unsigned(tx.gas_limit),
      tx.to,
      encode_unsigned(tx.value),
      if(tx.to == <<>>, do: tx.init, else: tx.data)
    ]

    if include_vrs do
      base ++
        [
          encode_unsigned(tx.v),
          encode_unsigned(tx.r),
          encode_unsigned(tx.s)
        ]
    else
      base
    end
  end

  @doc """
    iex(80)> :binary.encode_unsigned(12345)

    "09"

    iex(81)> "09" <> <<0>>

    <<48, 57, 0>>

    iex(83)> 48 * 256 + 57

    12345
  """
  @spec encode_unsigned(number()) :: binary()
  def encode_unsigned(0), do: <<>>
  def encode_unsigned(n), do: :binary.encode_unsigned(n)
priv =
  <<179, 57, 147, 246, 138, 161, 157, 91, 107, 216, 233, 48, 101, 29, 134, 144, 159, 60, 19, 74,
    2, 54, 0, 229, 207, 243, 60, 124, 244, 9, 123, 148>>

gas_price = 20_000_000_000
gas_limit = 300_000

tx =
  EthWallet.build_tx(
    "0x47ec2193b73b8b003645760df71569ae5e4b810c",
    1,
    <<>>,
    3,
    gas_price,
    gas_limit
  )

signed_tx = EthWallet.sign_tx(tx, priv)
EthWallet.signed_tx_to_raw_tx(signed_tx)
"0xf865038504a817c800830493e09447ec2193b73b8b003645760df71569ae5e4b810c01801ba094aa6fcd002671653c2ceb94d726f0916c3e6b1a136b3c27883625fe9eda99d8a07cc0d489bee5a6ed2e6373d2572472217adf5bfa057fc3cd018b201c376b04fd"

0x06 Send Transaction

! The func is impl by ethereumex, so I am not set it in wallet.

Check the api here:

https://infura.io/docs/ethereum/json-rpc/eth-sendRawTransaction

REQUEST PAYLOAD

  • RANSACTION DATA [required] - The signed transaction data. 
curl https://mainnet.infura.io/v3/YOUR-PROJECT-ID \
    -X POST \
    -H "Content-Type: application/json" \
    -d '{"jsonrpc":"2.0","method":"eth_sendRawTransaction","params":["0xd46e8dd67c5d32be8d46e8dd67c5d32be8058bb8eb970870f072445675058bb8eb970870f072445675"],"id":1}'

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