Ethereum Keys

A common API for Ethereum key operations with pluggable backends.

This library and repository was previously located at https://github.com/pipermerriam/ethereum-keys. It was transferred to the Ethereum foundation github in November 2017 and renamed to eth-keys. The PyPi package was also renamed from ethereum-keys to eth-keys.

Installation

pip install eth-keys

Development

pip install -e . -r requirements-dev.txt

Running the tests

You can run the tests with:

py.test tests

Or you can install tox to run the full test suite.

Releasing

Pandoc is required for transforming the markdown README to the proper format to render correctly on pypi.

For Debian-like systems:

apt install pandoc

Or on OSX:

brew install pandoc

To release a new version:

make release bump=$$VERSION_PART_TO_BUMP$$

How to bumpversion

The version format for this repo is {major}.{minor}.{patch} for stable, and {major}.{minor}.{patch}-{stage}.{devnum} for unstable (stage can be alpha or beta).

To issue the next version in line, specify which part to bump, like make release bump=minor or make release bump=devnum.

If you are in a beta version, make release bump=stage will switch to a stable.

To issue an unstable version when the current version is stable, specify the new version explicitly, like make release bump="--new-version 2.0.0-alpha.1 devnum"

QuickStart

>>> from eth_keys import keys
>>> pk = keys.PrivateKey(b'\x01' * 32)
>>> signature = pk.sign_msg(b'a message')
>>> pk
'0x0101010101010101010101010101010101010101010101010101010101010101'
>>> pk.public_key
'0x1b84c5567b126440995d3ed5aaba0565d71e1834604819ff9c17f5e9d5dd078f70beaf8f588b541507fed6a642c5ab42dfdf8120a7f639de5122d47a69a8e8d1'
>>> signature
'0xccda990dba7864b79dc49158fea269338a1cf5747bc4c4bf1b96823e31a0997e7d1e65c06c5bf128b7109e1b4b9ba8d1305dc33f32f624695b2fa8e02c12c1e000'
>>> pk.public_key.to_checksum_address()
'0x1a642f0E3c3aF545E7AcBD38b07251B3990914F1'
>>> signature.verify_msg(b'a message', pk.public_key)
True
>>> signature.recover_public_key_from_msg(b'a message') == pk.public_key
True

Documentation

KeyAPI(backend=None)

The KeyAPI object is the primary API for interacting with the eth-keys libary. The object takes a single optional argument in its constructor which designates what backend will be used for eliptical curve cryptography operations. The built-in backends are:

• eth_keys.backends.NativeECCBackend: A pure python implementation of the ECC operations.
• eth_keys.backends.CoinCurveECCBackend: Uses the coincurve library for ECC operations.

By default, eth-keys will try to use the CoinCurveECCBackend, falling back to the NativeECCBackend if the coincurve library is not available.

Note: The coincurve library is not automatically installed with eth-keys and must be installed separately.

The backend argument can be given in any of the following forms.

• Instance of the backend class
• The backend class
• String with the dot-separated import path for the backend class.

>>> from eth_keys import KeyAPI
>>> from eth_keys.backends import NativeECCBackend
# These are all the same
>>> keys = KeyAPI(NativeECCBackend)
>>> keys = KeyAPI(NativeECCBackend())
>>> keys = KeyAPI('eth_keys.backends.NativeECCBackend')
# Or for the coincurve base backend
>>> keys = KeyAPI('eth_keys.backends.CoinCurveECCBackend')

The backend can also be configured using the environment variable ECC_BACKEND_CLASS which should be set to the dot-separated python import path to the desired backend.

>>> import os
>>> os.environ['ECC_BACKEND_CLASS'] = 'eth_keys.backends.CoinCurveECCBackend'

KeyAPI.ecdsa_sign(message_hash, private_key) -> Signature

This method returns a signature for the given message_hash, signed by the provided private_key.

• message_hash: must be a byte string of length 32
• private_key: must be an instance of PrivateKey

KeyAPI.ecdsa_verify(message_hash, signature, public_key) -> bool

Returns True or False based on whether the provided signature is a valid signature for the provided message_hash and public_key.

• message_hash: must be a byte string of length 32
• signature: must be an instance of Signature
• public_key: must be an instance of PublicKey

KeyAPI.ecdsa_recover(message_hash, signature) -> PublicKey

Returns the PublicKey instances recovered from the given signature and message_hash.

• message_hash: must be a byte string of length 32
• signature: must be an instance of Signature

KeyAPI.private_key_to_public_key(private_key) -> PublicKey

Returns the PublicKey instances computed from the given private_key instance.

• private_key: must be an instance of PublicKey

Common APIs for PublicKey, PrivateKey and Signature

There is a common API for the following objects.

• PublicKey
• PrivateKey
• Signature

Each of these objects has all of the following APIs.

• obj.to_bytes(): Returns the object in it's canonical bytes serialization.
• obj.to_hex(): Returns a text string of the hex encoded canonical representation.

KeyAPI.PublicKey(public_key_bytes)

The PublicKey class takes a single argument which must be a bytes string with length 64.

Note that some libraries prefix the byte serialized public key with a leading \x04 byte which must be removed before use with the PublicKey object.

The following methods are available:

PublicKey.from_private(private_key) -> PublicKey

This classmethod returns a new PublicKey instance computed from the given private_key.

• private_key may either be a byte string of length 32 or an instance of the KeyAPI.PrivateKey class.

PublicKey.recover_from_msg(message, signature) -> PublicKey

This classmethod returns a new PublicKey instance computed from the provided message and signature.

• message must be a byte string
• signature must be an instance of KeyAPI.Signature

PublicKey.recover_from_msg_hash(message_hash, signature) -> PublicKey

Same as PublicKey.recover_from_msg except that message_hash should be the Keccak hash of the message.

PublicKey.verify_msg(message, signature) -> bool

This method returns True or False based on whether the signature is a valid for the given message.

PublicKey.verify_msg_hash(message_hash, signature) -> bool

Same as PublicKey.verify_msg except that message_hash should be the Keccak hash of the message.

PublicKey.to_address() -> text

Returns the hex encoded ethereum address for this public key.

PublicKey.to_checksum_address() -> text

Returns the ERC55 checksum formatted ethereum address for this public key.

PublicKey.to_canonical_address() -> bytes

Returns the 20-byte representation of the ethereum address for this public key.

KeyAPI.PrivateKey(private_key_bytes)

The PrivateKey class takes a single argument which must be a bytes string with length 32.

The following methods and properties are available

PrivateKey.public_key

This property holds the PublicKey instance coresponding to this private key.

PrivateKey.sign_msg(message) -> Signature

This method returns a signature for the given message in the form of a Signature instance

• message must be a byte string.

PrivateKey.sign_msg_hash(message_hash) -> Signature

Same as PrivateKey.sign except that message_hash should be the Keccak hash of the message.

KeyAPI.Signature(signature_bytes=None, vrs=None)

The Signature class can be instantiated in one of two ways.

• signature_bytes: a bytes string with length 65.
• vrs: a 3-tuple composed of the integers v, r, and s.

Note: If using the signature_bytes to instantiate, the byte string should be encoded as r_bytes | s_bytes | v_bytes where | represents concatenation. r_bytes and s_bytes should be 32 bytes in length. v_bytes should be a single byte \x00 or \x01.

Signatures are expected to use 1 or 0 for their v value.

The following methods and properties are available

Signature.v

This property returns the v value from the signature as an integer.

Signature.r

This property returns the r value from the signature as an integer.

Signature.s

This property returns the s value from the signature as an integer.

Signature.vrs

This property returns a 3-tuple of (v, r, s).

Signature.verify_msg(message, public_key) -> bool

This method returns True or False based on whether the signature is a valid for the given public key.

• message: must be a byte string.
• public_key: must be an instance of PublicKey

Signature.verify_msg_hash(message_hash, public_key) -> bool

Same as Signature.verify_msg except that message_hash should be the Keccak hash of the message.

Signature.recover_public_key_from_msg(message) -> PublicKey

This method returns a PublicKey instance recovered from the signature.

• message: must be a byte string.

Signature.recover_public_key_from_msg_hash(message_hash) -> PublicKey

Same as Signature.recover_public_key_from_msg except that message_hash should be the Keccak hash of the message.

Exceptions

eth_api.exceptions.ValidationError

This error is raised during instantaition of any of the PublicKey, PrivateKey or Signature classes if their constructor parameters are invalid.

eth_api.exceptions.BadSignature

This error is raised from any of the recover or verify methods involving signatures if the signature is invalid.