# Signet
[](https://github.com/hayesgm/signet/actions?query=workflow%3A%22Signet+Tests%22) [](https://hex.pm/packages/signet/) [](https://hexdocs.pm/signet/) [](https://hex.pm/packages/signet) [](https://github.com/hayesgm/signet/commits/main)
<img src="https://github.com/hayesgm/signet/raw/main/logo.png" width="100">
----
Signet is a lightweight Ethereum RPC client for Elixir. The goal is to make it easy to interact with Ethereum in Elixir. As an example:
```elixir
{:ok, trx_id} =
Signet.RPC.execute_trx(
"0x123...",
{"transfer(uint)", [50]},
gas_price: {50, :gwei},
value: 0
)
```
The above code will use a signer you set-up (see below) to send a build, sign and transmit a transaction to Infura. Signet handles determining your nonce and estimating the gas cost, and, by default, fails if the transaction were to revert.
Signet has a number of other features, including:
* Signing and verifying Ethereum signatures (including [EIP-191](https://eips.ethereum.org/EIPS/eip-191))
* Signing and verifying [EIP-712 typed data](https://eips.ethereum.org/EIPS/eip-712)
* Signing via [Curvy](https://github.com/libitx/curvy) or [Google KMS](https://cloud.google.com/kms/docs/apis).
* Note: Curvy signatures should be avoided in production.
* Filters through active processes
## Installation
Signet can be installed by adding `signet` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:signet, "~> 1.0.0-alpha5"}
]
end
```
Documentation can be found at <https://hexdocs.pm/signet>.
## Getting Started
### Signers
First, you'll need to set-up a signer, which will be used to sign transactions or other messages. Signers are GenServers, and uou can set-up several signers, and you will specify a name of a signer (or pid) at the point of actually using the signer. Currently there are two supported signers: raw keys or Google KMS.
#### Raw Key
** Note: This uses an experimental Elixir signing library, Curvy, and is considered unsafe for production. **
You can specify a signer key by configuring:
** runtime.exs **
```elixir
config :signet, :signer,
[{MySigner, {:priv_key, System.get_env("MY_PRIVATE_KEY")}}]
```
Then use `MySigner` when asked for a signer when using Signet.
You can also specify a default signer, which will be used by default so you do not need to specify the signer in your calls:
```elixir
config :signet, :signer, default: {:priv_key, System.get_env("MY_PRIVATE_KEY")}
```
#### Google KMS
You can set-up Google KMS by configuring:
```elixir
config :signet, :signer, [
{MySigner, {:cloud_kms, GCPCredentials, "projects/{project}/locations/{location}/keyRings/{keyring}/cryptoKeys/{keyid}", "1"}}]
```
This will use your given key from the URL, version "1", for signing.
`GCPCredentials` should be a `Goth` process set-up with proper credentials to access Google Cloud KMS.
#### Custom Signers
You can also specify custom signers by specifying an mfa that implements the required behavior:
```elixir
config :signet, :signers, %{
MySigner: {:mfa, Signet.Signer.Curvy, :sign, [<<1::256>>]}
}
```
Feel free to add pull requests with new signing methods.
You can also spawn your own process by adding to your start-up application:
```elixir
children = [
# ...
{Signet.Signer, mfa: {...}, chain_id: chain_id, name: MySigner}
]
```
Note: if you do not name your signer, it will be named `Signet.Signer.Default` and will be used to sign all transactions unless otherwise specified.
### Signing
Now that you have a signer, you can sign data, for instance:
```elixir
{:ok, sig} = Signet.Signer.sign("test", MySigner)
```
And then you can recover it via:
```elixir
signer_address = Signet.Recover.recover_eth("test", sig)
```
You can also sign EIP-712 typed data:
```elixir
%Signet.Typed{
domain: %Signet.Typed.Domain{
chain_id: 1,
name: "Ether Mail",
verifying_contract: Signet.Util.decode_hex!("0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"),
version: "1"
},
types: %{
"Mail" => %Signet.Typed.Type{fields: [{"from", "Person"}, {"to", "Person"}, {"contents", :string}]},
"Person" => %Signet.Typed.Type{fields: [{"name", :string}, {"wallet", :address}]}
},
value: %{
"contents" => "Hello, Bob!",
"from" => %{
"name" => "Cow",
"wallet" => Signet.Util.decode_hex!("0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826")
},
"to" => %{
"name" => "Bob",
"wallet" => Signet.Util.decode_hex!("0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB")
}
}
}
|> Signet.Typed.encode()
|> Signet.Signer.sign()
```
### RPC
Signet includes an RPC library to talk to Ethereum nodes, such as Infura. First, specify an Ethereum node address, e.g.
** config.exs **
```elixir
config :signet,
ethereum_node: "https://goerli.infura.io"
chain_id: :goerli
```
Then, you can run any Ethereum JSON-RPC command, e.g.:
```elixir
Signet.RPC.send_rpc("net_version", [])
{:ok, "3"}
```
You can build an Ethereum (pre-EIP-1559) transaction, e.g.:
```elixir
transaction = Signet.Transaction.V1.new(1, {100, :gwei}, 100_000, <<1::160>>, {2, :wei}, <<1, 2, 3>>)
```
And you can get the results from calling that transaction, via:
```elixir
{:ok, <<0x0c>>} = Signet.RPC.call_trx(transaction)
```
And if you're happy, you can send the trx:
```elixir
{:ok, trx_id} = Signet.RPC.send_trx(transaction)
```
You can also pass in known Solidity errors, to have them decoded for you, e.g.:
```elixir
> errors = ["Cool(uint256,string)"]
> Signet.Transaction.V1.new(1, {100, :gwei}, 100_000, <<11::160>>, {2, :wei}, <<1, 2, 3>>)
> |> Signet.RPC.call_trx(errors: errors)
{:error, "error 3: execution reverted (Cool(uint256,string)[1, \"cat\"])"}
```
Finally, `execute_trx` is similar to sending transactions with Web3, which will pull a nonce and estimate gas, before submitting the transaction to the Ethereum node:
```elixir
{:ok, trx_id} = Signet.RPC.execute_trx(<<1::160>>, {"baz(uint,address)", [50, <<1::160>> |> :binary.decode_unsigned]}, priority_fee: {2, :gwei}, gas_limit: 100_000, value: 0, nonce: 10)
```
Note: due to our ABI encoder, addresses should be passed in as `unsigned`s, not binaries.
You can pull a transaction receipt via:
```elixir
{:ok, receipt} = Signet.RPC.get_trx_receipt(trx_id)
```
You can pull a transaction traces via:
```elixir
{:ok, trace} = Signet.RPC.trace_transaction(trx_id)
```
### Filtering
The library also has a built-in system to use JSON-RPC filters (i.e. via `eth_newFilter`). In your application.ex (or any other supervisor), start a new filter:
```
children = [
# ...
# Filter name # Address # Topics
{Signet.Filter, [MyTransferFilter, <<1::160>>, [<<2::256>>]]}
]
```
Then, in your code, any process can register to hear events from the filter via:
```elixir
Signet.Filter.listen(MyTransferFilter)
```
Once registered, events will be passed in via Elixir messages `{:event, event}` for decoded events and `{:log, log}` for plain logs. For example:
```elixir
defmodule MyGenServer do
use GenServer
# ...
def init(_) do
Signet.Filter.listen(MyTransferFilter)
end
def handle_info({:event, event, log}, state) do
IO.inspect(event, label: "New Event")
{:noreply, state}
end
def handle_info({:log, log}, state) do
IO.inspect(log, label: "New Log")
{:noreply, state}
end
end
```
Currently, only ERC-20 transfer events as decoded, e.g. as:
```elixir
{:event, {"Transfer", %{"from" => <<1::160>>, "to" => <<2::160>>, "amount" => 100}}, %Signet.Filter.Log{}}
```
Note: filters may expire if not refreshed every so often. The filter code does not attempt to reach back in time if a filter is expired- that is up to your code.
## Keys
You can create Ethereum keys using Signet. These libraries are built on top of erlang's [crypto](https://www.erlang.org/doc/man/crypto.html) library, so they should be production safe, but you should be careful none-the-less when generating private keys in your app.
```elixir
> {address, priv_key} = Signet.Keys.generate_keypair()
> Signet.Util.encode_hex(address)
"0x3586B0916AC3C042A2B7E4A73841977941A69C4F"
> Signet.Util.encode_hex(priv_key)
"0x2EADD3966648553096523C38BB464E7DFDDD30293D02909FA2200FF571A90E85"
```
## Contributing
Create a PR to contribute to Signet. All contributors agree to accept the license specified in this repository for all contributions to this project. See [LICENSE.md](/LICENSE.md).
Feel free to create Feature Requests in the issues.
Note: The author generated the Signet logo with DALL•E, OpenAI's text-to-image generation model. The image was further modified by the author.
