Keypair creation and signing
============================

.. toctree::
   :maxdepth: 4

Keypairs are used to sign transactions and encrypt/decrypt messages.
They consist of a public/private key and can be generated in several
ways like by a BIP39 mnemonic:

.. code:: python

   mnemonic = Keypair.generate_mnemonic()
   keypair = Keypair.create_from_mnemonic(mnemonic)
   signature = keypair.sign("Test123")
   if keypair.verify("Test123", signature):
       print('Verified')

By default, a keypair is using
`SR25519 <https://research.web3.foundation/en/latest/polkadot/keys/1-accounts-more.html>`__
cryptography, alternatively ED25519 and ECDSA (for Ethereum-style
addresses) can be explicitly specified:

.. code:: python

   keypair = Keypair.create_from_mnemonic(mnemonic, crypto_type=KeypairType.ECDSA)
   print(keypair.ss58_address)
   # '0x6741864968e8b87c6e32e19cde88A11a3Cc636E9'

**Creating keypairs with soft and hard key derivation paths**

.. code:: python

   mnemonic = Keypair.generate_mnemonic()
   keypair = Keypair.create_from_uri(mnemonic + '//hard/soft')

By omitting the mnemonic the default development mnemonic is used:

.. code:: python

   keypair = Keypair.create_from_uri('//Alice')

**Creating ECDSA keypairs with BIP44 derivation paths**

.. code:: python

   mnemonic = Keypair.generate_mnemonic()
   keypair = Keypair.create_from_uri(f"{mnemonic}/m/44'/60'/0'/0/0", crypto_type=KeypairType.ECDSA)

**Create Keypair from PolkadotJS JSON format**

.. code:: python

   with open('5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY.json', 'r') as fp:
       json_data = fp.read()
       keypair = Keypair.create_from_encrypted_json(json_data, passphrase="test", ss58_format=42)

**Verify generated signature with public address**

*Example: Substrate style addresses*

.. code:: python

   keypair = Keypair.create_from_uri("//Alice", crypto_type=KeypairType.SR25519)
   signature = keypair.sign('test')

   keypair_public = Keypair(ss58_address='5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY', crypto_type=KeypairType.SR25519)
   result = keypair_public.verify('test', signature)

*Example: Ethereum style addresses*

.. code:: python

   keypair = Keypair.create_from_uri("/m/44'/60/0'/0", crypto_type=KeypairType.ECDSA)
   signature = keypair.sign('test')

   keypair_public = Keypair(public_key='0x5e20a619338338772e97aa444e001043da96a43b', crypto_type=KeypairType.ECDSA)
   result = keypair_public.verify('test', signature)

**Offline signing of extrinsics**

This example generates a signature payload which can be signed on
another (offline) machine and later on sent to the network with the
generated signature.

1. Generate signature payload on online machine:

.. code:: python

   portaldot = SubstrateInterface(
         url="wss://mainnet.portaldot.io",
         ss58_format=42,
         type_registry_preset='default'
      )

   call = portaldot.compose_call(
       call_module='Balances',
       call_function='transfer_keep_alive',
       call_params={
           'dest': '5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY',
           'value': 2 * 10**8
       }
   )

   era = {'period': 64, 'current': 22719}
   nonce = 0

   signature_payload = portaldot.generate_signature_payload(call=call, era=era, nonce=nonce)

2. Then on another (offline) machine generate the signature with given
   ``signature_payload``:

.. code:: python

   keypair = Keypair.create_from_mnemonic("nature exchange gasp toy result bacon coin broccoli rule oyster believe lyrics")
   signature = keypair.sign(signature_payload)

3. Finally on the online machine send the extrinsic with generated
   signature:

.. code:: python

   keypair = Keypair(ss58_address="5EChUec3ZQhUvY1g52ZbfBVkqjUY9Kcr6mcEvQMbmd38shQL")

   extrinsic = portaldot.create_signed_extrinsic(
       call=call,
       keypair=keypair,
       era=era,
       nonce=nonce,
       signature=signature
   )

   result = portaldot.submit_extrinsic(
       extrinsic=extrinsic
   )

   print(result.extrinsic_hash)