Onchain.Signer (onchain v0.5.0)

EIP-1559 transaction building, signing, encoding, and broadcasting.

Stateless pipeline — no GenServer, no application config. Private key is always passed explicitly. Uses Signet.Signer.sign_direct/4 for signing and Signet.Transaction.V2 for transaction construction.

Pipeline

build_transaction/3 → sign_transaction/3 → encode_transaction/1 → RPC.eth_send_raw_transaction/2

Or use send_transaction/3 for the full pipeline in one call.

Functions

Function	Purpose
`address_from_key/1`	Derive checksummed address from private key
`build_transaction/3`	Build unsigned EIP-1559 transaction
`sign_transaction/3`	Sign transaction with private key
`encode_transaction/1`	Encode signed transaction to hex
`send_transaction/3`	Full pipeline: build → sign → encode → broadcast

API Functions

Function	Arity	Description	Param Kinds
`send_transaction!`	3	Build, sign, encode, and broadcast a transaction in one call. Raises on error.	`to: value`, `calldata: value`, `opts: value`
`send_transaction`	3	Build, sign, encode, and broadcast a transaction in one call.	`to: value`, `calldata: value`, `opts: value`
`encode_transaction!`	1	Encode a signed transaction to 0x-prefixed hex for broadcast. Raises on error.	`signed_trx: value`
`encode_transaction`	1	Encode a signed transaction to 0x-prefixed hex for broadcast.	`signed_trx: value`
`sign_transaction!`	3	Sign a transaction with a private key. Raises on error.	`unsigned_trx: value`, `private_key: value`, `chain_id: value`
`sign_transaction`	3	Sign a transaction with a private key.	`unsigned_trx: value`, `private_key: value`, `chain_id: value`
`build_transaction!`	3	Build an unsigned EIP-1559 transaction. Raises on error.	`to: value`, `calldata: value`, `opts: value`
`build_transaction`	3	Build an unsigned EIP-1559 transaction.	`to: value`, `calldata: value`, `opts: value`
`address_from_key!`	1	Derive checksummed Ethereum address from a private key. Raises on error.	`private_key: value`
`address_from_key`	1	Derive checksummed Ethereum address from a private key.	`private_key: value`

Summary

Functions

address_from_key(private_key)

Derive checksummed Ethereum address from a private key.

address_from_key!(private_key)

Derive checksummed Ethereum address from a private key. Raises on error.

build_transaction(to, calldata, opts)

Build an unsigned EIP-1559 transaction.

build_transaction!(to, calldata, opts)

Build an unsigned EIP-1559 transaction. Raises on error.

encode_transaction(signed_trx)

Encode a signed transaction to 0x-prefixed hex for broadcast.

encode_transaction!(trx)

Encode a signed transaction to 0x-prefixed hex for broadcast. Raises on error.

send_transaction(to, calldata, opts)

Build, sign, encode, and broadcast a transaction in one call.

send_transaction!(to, calldata, opts)

Build, sign, encode, and broadcast a transaction in one call. Raises on error.

sign_transaction(unsigned_trx, private_key, chain_id)

Sign a transaction with a private key.

sign_transaction!(unsigned_trx, private_key, chain_id)

Sign a transaction with a private key. Raises on error.

Functions

address_from_key(private_key)

@spec address_from_key(binary()) ::
  {:ok, String.t()} | {:error, {:invalid_private_key, term()}}

Derive checksummed Ethereum address from a private key.

Parameters

private_key - 32-byte binary or hex string (with or without 0x) (value)

Returns

EIP-55 checksummed address ({:ok, String.t()} | {:error, {:invalid_private_key, term()}})

# descripex:contract
%{
  params: %{
    private_key: %{
      description: "32-byte binary or hex string (with or without 0x)",
      kind: :value
    }
  },
  returns: %{
    type: "{:ok, String.t()} | {:error, {:invalid_private_key, term()}}",
    description: "EIP-55 checksummed address",
    example: "0x63Cc7c25e0cdb121aBb0fE477a6b9901889F99A7"
  }
}

address_from_key!(private_key)

@spec address_from_key!(binary()) :: String.t()

Derive checksummed Ethereum address from a private key. Raises on error.

Parameters

private_key - 32-byte binary or hex string (with or without 0x) (value)

Returns

EIP-55 checksummed address (string)

# descripex:contract
%{
  params: %{
    private_key: %{
      description: "32-byte binary or hex string (with or without 0x)",
      kind: :value
    }
  },
  returns: %{type: :string, description: "EIP-55 checksummed address"}
}

build_transaction(to, calldata, opts)

@spec build_transaction(binary(), binary() | {:raw, binary()}, keyword()) ::
  {:ok, Signet.Transaction.V2.t()} | {:error, term()}

Build an unsigned EIP-1559 transaction.

Parameters

to - Destination address (hex string or 20-byte binary) (value)
calldata - Raw binary calldata (use Hex.decode!/1 on ABI.encode_call output), {:raw, binary} for literal bytes that start with 0x, or <<>> for plain ETH transfer (value)
opts - Required: :nonce, :chain_id. Optional: :gas_limit, :max_fee_per_gas, :max_priority_fee_per_gas, :value, :access_list. Gas params accept integers (wei) or {n, :gwei} tuples. (value)

Returns

Unsigned EIP-1559 transaction struct ({:ok, %Signet.Transaction.V2{}} | {:error, term()})

# descripex:contract
%{
  params: %{
    opts: %{
      description: "Required: :nonce, :chain_id. Optional: :gas_limit, :max_fee_per_gas, :max_priority_fee_per_gas, :value, :access_list. Gas params accept integers (wei) or {n, :gwei} tuples.",
      kind: :value
    },
    to: %{
      description: "Destination address (hex string or 20-byte binary)",
      kind: :value
    },
    calldata: %{
      description: "Raw binary calldata (use Hex.decode!/1 on ABI.encode_call output), {:raw, binary} for literal bytes that start with 0x, or <<>> for plain ETH transfer",
      kind: :value
    }
  },
  returns: %{
    type: "{:ok, %Signet.Transaction.V2{}} | {:error, term()}",
    description: "Unsigned EIP-1559 transaction struct"
  }
}

build_transaction!(to, calldata, opts)

@spec build_transaction!(binary(), binary() | {:raw, binary()}, keyword()) ::
  Signet.Transaction.V2.t()

Build an unsigned EIP-1559 transaction. Raises on error.

Parameters

to - Destination address (hex string or 20-byte binary) (value)
calldata - Raw binary calldata (use Hex.decode!/1 on ABI.encode_call output), {:raw, binary} for literal bytes that start with 0x, or <<>> for plain ETH transfer (value)
opts - Required: :nonce, :chain_id. Optional: :gas_limit, :max_fee_per_gas, :max_priority_fee_per_gas, :value, :access_list. Gas params accept integers (wei) or {n, :gwei} tuples. (value)

Returns

Unsigned EIP-1559 transaction struct (%Signet.Transaction.V2{})

# descripex:contract
%{
  params: %{
    opts: %{
      description: "Required: :nonce, :chain_id. Optional: :gas_limit, :max_fee_per_gas, :max_priority_fee_per_gas, :value, :access_list. Gas params accept integers (wei) or {n, :gwei} tuples.",
      kind: :value
    },
    to: %{
      description: "Destination address (hex string or 20-byte binary)",
      kind: :value
    },
    calldata: %{
      description: "Raw binary calldata (use Hex.decode!/1 on ABI.encode_call output), {:raw, binary} for literal bytes that start with 0x, or <<>> for plain ETH transfer",
      kind: :value
    }
  },
  returns: %{
    type: "%Signet.Transaction.V2{}",
    description: "Unsigned EIP-1559 transaction struct"
  }
}

encode_transaction(signed_trx)

@spec encode_transaction(Signet.Transaction.V2.t()) ::
  {:ok, String.t()} | {:error, {:encode_error, :unsigned_transaction}}

Encode a signed transaction to 0x-prefixed hex for broadcast.

Parameters

signed_trx - Signed %Signet.Transaction.V2{} struct (value)

Returns

0x-prefixed hex string ready for eth_sendRawTransaction ({:ok, String.t()} | {:error, {:encode_error, :unsigned_transaction}})

# descripex:contract
%{
  params: %{
    signed_trx: %{
      description: "Signed %Signet.Transaction.V2{} struct",
      kind: :value
    }
  },
  returns: %{
    type: "{:ok, String.t()} | {:error, {:encode_error, :unsigned_transaction}}",
    description: "0x-prefixed hex string ready for eth_sendRawTransaction",
    example: "0x02f8..."
  }
}

encode_transaction!(trx)

@spec encode_transaction!(Signet.Transaction.V2.t()) :: String.t()

Encode a signed transaction to 0x-prefixed hex for broadcast. Raises on error.

Parameters

signed_trx - Signed %Signet.Transaction.V2{} struct (value)

Returns

0x-prefixed hex string ready for broadcast (string)

# descripex:contract
%{
  params: %{
    signed_trx: %{
      description: "Signed %Signet.Transaction.V2{} struct",
      kind: :value
    }
  },
  returns: %{
    type: :string,
    description: "0x-prefixed hex string ready for broadcast"
  }
}

send_transaction(to, calldata, opts)

@spec send_transaction(binary(), binary() | {:raw, binary()}, keyword()) ::
  {:ok, String.t()} | {:error, term()}

Build, sign, encode, and broadcast a transaction in one call.

Parameters

to - Destination address (hex string or 20-byte binary) (value)
calldata - Raw binary calldata (use Hex.decode!/1 on ABI.encode_call output), {:raw, binary} for literal bytes that start with 0x, or <<>> for plain ETH transfer (value)
opts - Required: :private_key, :nonce, :chain_id, :rpc_url. Optional: :gas_limit, :max_fee_per_gas, :max_priority_fee_per_gas, :value, :access_list (value)

Returns

Transaction hash hex string ({:ok, String.t()} | {:error, term()})

# descripex:contract
%{
  params: %{
    opts: %{
      description: "Required: :private_key, :nonce, :chain_id, :rpc_url. Optional: :gas_limit, :max_fee_per_gas, :max_priority_fee_per_gas, :value, :access_list",
      kind: :value
    },
    to: %{
      description: "Destination address (hex string or 20-byte binary)",
      kind: :value
    },
    calldata: %{
      description: "Raw binary calldata (use Hex.decode!/1 on ABI.encode_call output), {:raw, binary} for literal bytes that start with 0x, or <<>> for plain ETH transfer",
      kind: :value
    }
  },
  returns: %{
    type: "{:ok, String.t()} | {:error, term()}",
    description: "Transaction hash hex string"
  }
}

send_transaction!(to, calldata, opts)

@spec send_transaction!(binary(), binary() | {:raw, binary()}, keyword()) ::
  String.t()

Build, sign, encode, and broadcast a transaction in one call. Raises on error.

Parameters

to - Destination address (hex string or 20-byte binary) (value)
calldata - Raw binary calldata (use Hex.decode!/1 on ABI.encode_call output), {:raw, binary} for literal bytes that start with 0x, or <<>> for plain ETH transfer (value)
opts - Required: :private_key, :nonce, :chain_id, :rpc_url. Optional: :gas_limit, :max_fee_per_gas, :max_priority_fee_per_gas, :value, :access_list (value)

Returns

Transaction hash hex string (string)

# descripex:contract
%{
  params: %{
    opts: %{
      description: "Required: :private_key, :nonce, :chain_id, :rpc_url. Optional: :gas_limit, :max_fee_per_gas, :max_priority_fee_per_gas, :value, :access_list",
      kind: :value
    },
    to: %{
      description: "Destination address (hex string or 20-byte binary)",
      kind: :value
    },
    calldata: %{
      description: "Raw binary calldata (use Hex.decode!/1 on ABI.encode_call output), {:raw, binary} for literal bytes that start with 0x, or <<>> for plain ETH transfer",
      kind: :value
    }
  },
  returns: %{type: :string, description: "Transaction hash hex string"}
}

sign_transaction(unsigned_trx, private_key, chain_id)

@spec sign_transaction(Signet.Transaction.V2.t(), binary(), pos_integer()) ::
  {:ok, Signet.Transaction.V2.t()}
  | {:error, {:sign_error, term()} | {:invalid_private_key, term()}}

Sign a transaction with a private key.

Parameters

unsigned_trx - Unsigned %Signet.Transaction.V2{} struct (value)
private_key - 32-byte binary or hex string (with or without 0x) (value)
chain_id - Chain ID integer (1 = mainnet, 11155111 = Sepolia) (value)

Returns

Signed transaction with signature fields populated ({:ok, %Signet.Transaction.V2{}} | {:error, {:sign_error, term()}})

# descripex:contract
%{
  params: %{
    private_key: %{
      description: "32-byte binary or hex string (with or without 0x)",
      kind: :value
    },
    chain_id: %{
      description: "Chain ID integer (1 = mainnet, 11155111 = Sepolia)",
      kind: :value
    },
    unsigned_trx: %{
      description: "Unsigned %Signet.Transaction.V2{} struct",
      kind: :value
    }
  },
  returns: %{
    type: "{:ok, %Signet.Transaction.V2{}} | {:error, {:sign_error, term()}}",
    description: "Signed transaction with signature fields populated"
  }
}

sign_transaction!(unsigned_trx, private_key, chain_id)

@spec sign_transaction!(Signet.Transaction.V2.t(), binary(), pos_integer()) ::
  Signet.Transaction.V2.t()

Sign a transaction with a private key. Raises on error.

Parameters

unsigned_trx - Unsigned %Signet.Transaction.V2{} struct (value)
private_key - 32-byte binary or hex string (with or without 0x) (value)
chain_id - Chain ID integer (1 = mainnet, 11155111 = Sepolia) (value)

Returns

Signed transaction with signature fields populated (%Signet.Transaction.V2{})

# descripex:contract
%{
  params: %{
    private_key: %{
      description: "32-byte binary or hex string (with or without 0x)",
      kind: :value
    },
    chain_id: %{
      description: "Chain ID integer (1 = mainnet, 11155111 = Sepolia)",
      kind: :value
    },
    unsigned_trx: %{
      description: "Unsigned %Signet.Transaction.V2{} struct",
      kind: :value
    }
  },
  returns: %{
    type: "%Signet.Transaction.V2{}",
    description: "Signed transaction with signature fields populated"
  }
}