ethereum.byzantium.vm.precompiled_contracts.ecrecoverethereum.constantinople.vm.precompiled_contracts.ecrecover

Ethereum Virtual Machine (EVM) ECRECOVER PRECOMPILED CONTRACT ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. contents:: Table of Contents :backlinks: none :local:

Introduction

Implementation of the ECRECOVER precompiled contract.

ecrecover

Decrypts the address using elliptic curve DSA recovery mechanism and writes the address to output.

Parameters

evm : The current EVM frame.

def ecrecover(​evm: Evm​) -> None:
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    """
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    Decrypts the address using elliptic curve DSA recovery mechanism and writes
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    the address to output.
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    Parameters
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    ----------
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    evm :
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        The current EVM frame.
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    """
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    data = evm.message.data
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    # GAS
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    charge_gas(evm, GAS_ECRECOVER)
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    # OPERATION
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    message_hash_bytes = buffer_read(data, U256(0), U256(32))
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    message_hash = Hash32(message_hash_bytes)
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    v = U256.from_be_bytes(buffer_read(data, U256(32), U256(32)))
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    r = U256.from_be_bytes(buffer_read(data, U256(64), U256(32)))
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    s = U256.from_be_bytes(buffer_read(data, U256(96), U256(32)))
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    if v != U256(27) and v != U256(28):
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        return
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    if U256(0) >= r or r >= SECP256K1N:
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        return
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    if U256(0) >= s or s >= SECP256K1N:
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        return
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    try:
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        public_key = secp256k1_recover(r, s, v - U256(27), message_hash)
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    except ValueError:
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        # unable to extract public key
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        return
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    address = keccak256(public_key)[12:32]
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    padded_address = left_pad_zero_bytes(address, 32)
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    evm.output = padded_address