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Entropy (η)

Bases: StateComponent

Source code in pyjamaz/state/components.py 
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class Entropy(StateComponent):
    component_id = 6

    @log_execution_time
    def state_transition(
            self,
            header: Header,
            pre_state_timeslot: TimeslotState,
            pre_state_entropy: EntropyState
    ) -> EntropyOutput:
        """
        GP-0.7.2-eq:6.22,6.23 (η') | State transition function for the state's entropy.

        Parameters
        ----------
        header: Header
            GP-0.7.2-eq:4.8 (bold_H)
        pre_state_timeslot: TimeslotState
            GP-0.7.2-eq:4.8 (τ)
        pre_state_entropy: EntropyState
            GP-0.7.2-eq:4.8 (η)

        Returns
        -------
        EntropyOutput
            Output containing: posterior state of EntropyState (η')
        """

        post_state_entropy = deepcopy(pre_state_entropy)

        # GP-0.7.2-eq:6.22 (η'[0]) | State transition for first index of the entropy.
        eta_0 = blake2b_256_hash(pre_state_entropy.entropy[0] + self.entropy_output(header))

        # GP-0.7.2-eq:6.23 (η'[1-3]) | State transition for last three indices of the entropy.
        # State transition happen on epoch change.
        if self.is_epoch_change(pre_state_timeslot.number, header.timeslot):
            # GP-0.7.2-eq:6.23 (`e > e'`) | When epoch changes
            post_state_entropy.entropy = [eta_0] + pre_state_entropy.entropy[:3]
        else:
            post_state_entropy.entropy = [eta_0] + pre_state_entropy.entropy[1:]

        return EntropyOutput(
            post_state=post_state_entropy
        )

    def retrieve_state(self) -> EntropyState:
        value = self.retrieve()
        return EntropyState.from_jam_bytes(JamBytes(value))

    @log_execution_time
    def entropy_output(self, header: Header) -> bytes:
        """
        GP-0.7.2-eq:G.5
        TODO check if output is indeed the first 32 bytes or a hash of the first 32 bytes
        TODO refactor to vrf_output of entropy signature
        Parameters
        ----------
        header: Header

        Returns
        -------
        bytes
        """

        if len(header.entropy_source) == 32:
            return header.entropy_source

        if header.author_bandersnatch_key is None or self.block_context.seal_vrf_output == bytes(96):
            return bytes(32)

        DEBUG and logging.debug(f"Verifying entropy source signature: bs_key={format_hash(bytes(header.author_bandersnatch_key))} vrf_output={format_hash(self.block_context.seal_vrf_output)}")
        try:
            return ietf_vrf_verify(
                bytes(header.author_bandersnatch_key),
                b"jam_entropy" + self.block_context.seal_vrf_output,
                b'',
                bytes(header.entropy_source)
            )
        except ValueError:
            raise BlockValidationError("Invalid entropy source signature")

state_transition(header: Header, pre_state_timeslot: TimeslotState, pre_state_entropy: EntropyState) -> EntropyOutput

GP-0.7.2-eq:6.22,6.23 (η') | State transition function for the state's entropy.

Parameters:

Name Type Description Default
header Header

GP-0.7.2-eq:4.8 (bold_H)

 required
pre_state_timeslot TimeslotState

GP-0.7.2-eq:4.8 (τ)

 required
pre_state_entropy EntropyState

GP-0.7.2-eq:4.8 (η)

 required

Returns:

Type Description
EntropyOutput

Output containing: posterior state of EntropyState (η')
Source code in pyjamaz/state/components.py 
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@log_execution_time
def state_transition(
        self,
        header: Header,
        pre_state_timeslot: TimeslotState,
        pre_state_entropy: EntropyState
) -> EntropyOutput:
    """
    GP-0.7.2-eq:6.22,6.23 (η') | State transition function for the state's entropy.

    Parameters
    ----------
    header: Header
        GP-0.7.2-eq:4.8 (bold_H)
    pre_state_timeslot: TimeslotState
        GP-0.7.2-eq:4.8 (τ)
    pre_state_entropy: EntropyState
        GP-0.7.2-eq:4.8 (η)

    Returns
    -------
    EntropyOutput
        Output containing: posterior state of EntropyState (η')
    """

    post_state_entropy = deepcopy(pre_state_entropy)

    # GP-0.7.2-eq:6.22 (η'[0]) | State transition for first index of the entropy.
    eta_0 = blake2b_256_hash(pre_state_entropy.entropy[0] + self.entropy_output(header))

    # GP-0.7.2-eq:6.23 (η'[1-3]) | State transition for last three indices of the entropy.
    # State transition happen on epoch change.
    if self.is_epoch_change(pre_state_timeslot.number, header.timeslot):
        # GP-0.7.2-eq:6.23 (`e > e'`) | When epoch changes
        post_state_entropy.entropy = [eta_0] + pre_state_entropy.entropy[:3]
    else:
        post_state_entropy.entropy = [eta_0] + pre_state_entropy.entropy[1:]

    return EntropyOutput(
        post_state=post_state_entropy
    )

entropy_output(header: Header) -> bytes

GP-0.7.2-eq:G.5 TODO check if output is indeed the first 32 bytes or a hash of the first 32 bytes TODO refactor to vrf_output of entropy signature

Parameters:

Name Type Description Default
header Header
required

Returns:

Type Description
bytes
Source code in pyjamaz/state/components.py 
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@log_execution_time
def entropy_output(self, header: Header) -> bytes:
    """
    GP-0.7.2-eq:G.5
    TODO check if output is indeed the first 32 bytes or a hash of the first 32 bytes
    TODO refactor to vrf_output of entropy signature
    Parameters
    ----------
    header: Header

    Returns
    -------
    bytes
    """

    if len(header.entropy_source) == 32:
        return header.entropy_source

    if header.author_bandersnatch_key is None or self.block_context.seal_vrf_output == bytes(96):
        return bytes(32)

    DEBUG and logging.debug(f"Verifying entropy source signature: bs_key={format_hash(bytes(header.author_bandersnatch_key))} vrf_output={format_hash(self.block_context.seal_vrf_output)}")
    try:
        return ietf_vrf_verify(
            bytes(header.author_bandersnatch_key),
            b"jam_entropy" + self.block_context.seal_vrf_output,
            b'',
            bytes(header.entropy_source)
        )
    except ValueError:
        raise BlockValidationError("Invalid entropy source signature")