ethereum.byzantium.vm.precompiled_contracts.alt_bn128ethereum.constantinople.vm.precompiled_contracts.alt_bn128

Ethereum Virtual Machine (EVM) ALT_BN128 CONTRACTS ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

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

Introduction

Implementation of the ALT_BN128 precompiled contracts.

alt_bn128_add

The ALT_BN128 addition precompiled contract.

Parameters

evm : The current EVM frame.

def alt_bn128_add(​evm: Evm​) -> None:
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    """
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    The ALT_BN128 addition precompiled contract.
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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, Uint(500))
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    # OPERATION
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    x0_bytes = buffer_read(data, U256(0), U256(32))
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    x0_value = int(U256.from_be_bytes(x0_bytes))
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    y0_bytes = buffer_read(data, U256(32), U256(32))
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    y0_value = int(U256.from_be_bytes(y0_bytes))
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    x1_bytes = buffer_read(data, U256(64), U256(32))
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    x1_value = int(U256.from_be_bytes(x1_bytes))
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    y1_bytes = buffer_read(data, U256(96), U256(32))
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    y1_value = int(U256.from_be_bytes(y1_bytes))
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    for i in (x0_value, y0_value, x1_value, y1_value):
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        if i >= ALT_BN128_PRIME:
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            raise OutOfGasError
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    try:
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        p0 = BNP(BNF(x0_value), BNF(y0_value))
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        p1 = BNP(BNF(x1_value), BNF(y1_value))
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    except ValueError:
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        raise OutOfGasError
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    p = p0 + p1
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    evm.output = p.x.to_be_bytes32() + p.y.to_be_bytes32()

alt_bn128_mul

The ALT_BN128 multiplication precompiled contract.

Parameters

evm : The current EVM frame.

def alt_bn128_mul(​evm: Evm​) -> None:
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    """
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    The ALT_BN128 multiplication precompiled contract.
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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, Uint(40000))
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    # OPERATION
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    x0_bytes = buffer_read(data, U256(0), U256(32))
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    x0_value = int(U256.from_be_bytes(x0_bytes))
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    y0_bytes = buffer_read(data, U256(32), U256(32))
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    y0_value = int(U256.from_be_bytes(y0_bytes))
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    n = int(U256.from_be_bytes(buffer_read(data, U256(64), U256(32))))
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    for i in (x0_value, y0_value):
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        if i >= ALT_BN128_PRIME:
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            raise OutOfGasError
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    try:
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        p0 = BNP(BNF(x0_value), BNF(y0_value))
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    except ValueError:
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        raise OutOfGasError
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    p = p0.mul_by(n)
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    evm.output = p.x.to_be_bytes32() + p.y.to_be_bytes32()

alt_bn128_pairing_check

The ALT_BN128 pairing check precompiled contract.

Parameters

evm : The current EVM frame.

def alt_bn128_pairing_check(​evm: Evm​) -> None:
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    """
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    The ALT_BN128 pairing check precompiled contract.
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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, Uint(80000 * (len(data) // 192) + 100000))
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    # OPERATION
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    if len(data) % 192 != 0:
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        raise OutOfGasError
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    result = BNF12.from_int(1)
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    for i in range(len(data) // 192):
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        values = []
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        for j in range(6):
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            value = int(
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                U256.from_be_bytes(
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                    data[i * 192 + 32 * j : i * 192 + 32 * (j + 1)]
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                )
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            )
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            if value >= ALT_BN128_PRIME:
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                raise OutOfGasError
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            values.append(value)
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        try:
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            p = BNP(BNF(values[0]), BNF(values[1]))
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            q = BNP2(
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                BNF2((values[3], values[2])), BNF2((values[5], values[4]))
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            )
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        except ValueError:
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            raise OutOfGasError()
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        if p.mul_by(ALT_BN128_CURVE_ORDER) != BNP.point_at_infinity():
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            raise OutOfGasError
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        if q.mul_by(ALT_BN128_CURVE_ORDER) != BNP2.point_at_infinity():
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            raise OutOfGasError
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        if p != BNP.point_at_infinity() and q != BNP2.point_at_infinity():
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            result = result * pairing(q, p)
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    if result == BNF12.from_int(1):
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        evm.output = U256(1).to_be_bytes32()
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    else:
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        evm.output = U256(0).to_be_bytes32()