Babe¶

Calls¶

plan_config_change¶

Plan an epoch config change. The epoch config change is recorded and will be enacted on the next call to enact_epoch_change. The config will be activated one epoch after. Multiple calls to this method will replace any existing planned config change that had not been enacted yet.

Attributes¶

Name	Type
config	`NextConfigDescriptor`

Python¶

call = substrate.compose_call(
    'Babe', 'plan_config_change', {
    'config': {
        None: None,
        'V1': {
            'allowed_slots': (
                'PrimarySlots',
                'PrimaryAndSecondaryPlainSlots',
                'PrimaryAndSecondaryVRFSlots',
            ),
            'c': ('u64', 'u64'),
        },
    },
}
)

report_equivocation¶

Report authority equivocation/misbehavior. This method will verify the equivocation proof and validate the given key ownership proof against the extracted offender. If both are valid, the offence will be reported.

Attributes¶

Name	Type
equivocation_proof	`Box<EquivocationProof<T::Header>>`
key_owner_proof	`T::KeyOwnerProof`

Python¶

call = substrate.compose_call(
    'Babe', 'report_equivocation', {
    'equivocation_proof': {
        'first_header': {
            'digest': {
                'logs': [
                    {
                        'Other': 'Bytes',
                        None: None,
                        'Consensus': (
                            '[u8; 4]',
                            'Bytes',
                        ),
                        'PreRuntime': (
                            '[u8; 4]',
                            'Bytes',
                        ),
                        'RuntimeEnvironmentUpdated': None,
                        'Seal': (
                            '[u8; 4]',
                            'Bytes',
                        ),
                    },
                ],
            },
            'extrinsics_root': 'scale_info::11',
            'number': 'u32',
            'parent_hash': 'scale_info::11',
            'state_root': 'scale_info::11',
        },
        'offender': '[u8; 32]',
        'second_header': {
            'digest': {
                'logs': [
                    {
                        'Other': 'Bytes',
                        None: None,
                        'Consensus': (
                            '[u8; 4]',
                            'Bytes',
                        ),
                        'PreRuntime': (
                            '[u8; 4]',
                            'Bytes',
                        ),
                        'RuntimeEnvironmentUpdated': None,
                        'Seal': (
                            '[u8; 4]',
                            'Bytes',
                        ),
                    },
                ],
            },
            'extrinsics_root': 'scale_info::11',
            'number': 'u32',
            'parent_hash': 'scale_info::11',
            'state_root': 'scale_info::11',
        },
        'slot': 'u64',
    },
    'key_owner_proof': {
        'session': 'u32',
        'trie_nodes': ['Bytes'],
        'validator_count': 'u32',
    },
}
)

report_equivocation_unsigned¶

Report authority equivocation/misbehavior. This method will verify the equivocation proof and validate the given key ownership proof against the extracted offender. If both are valid, the offence will be reported. This extrinsic must be called unsigned and it is expected that only block authors will call it (validated in ValidateUnsigned), as such if the block author is defined it will be defined as the equivocation reporter.

Attributes¶

Name	Type
equivocation_proof	`Box<EquivocationProof<T::Header>>`
key_owner_proof	`T::KeyOwnerProof`

Python¶

call = substrate.compose_call(
    'Babe', 'report_equivocation_unsigned', {
    'equivocation_proof': {
        'first_header': {
            'digest': {
                'logs': [
                    {
                        'Other': 'Bytes',
                        None: None,
                        'Consensus': (
                            '[u8; 4]',
                            'Bytes',
                        ),
                        'PreRuntime': (
                            '[u8; 4]',
                            'Bytes',
                        ),
                        'RuntimeEnvironmentUpdated': None,
                        'Seal': (
                            '[u8; 4]',
                            'Bytes',
                        ),
                    },
                ],
            },
            'extrinsics_root': 'scale_info::11',
            'number': 'u32',
            'parent_hash': 'scale_info::11',
            'state_root': 'scale_info::11',
        },
        'offender': '[u8; 32]',
        'second_header': {
            'digest': {
                'logs': [
                    {
                        'Other': 'Bytes',
                        None: None,
                        'Consensus': (
                            '[u8; 4]',
                            'Bytes',
                        ),
                        'PreRuntime': (
                            '[u8; 4]',
                            'Bytes',
                        ),
                        'RuntimeEnvironmentUpdated': None,
                        'Seal': (
                            '[u8; 4]',
                            'Bytes',
                        ),
                    },
                ],
            },
            'extrinsics_root': 'scale_info::11',
            'number': 'u32',
            'parent_hash': 'scale_info::11',
            'state_root': 'scale_info::11',
        },
        'slot': 'u64',
    },
    'key_owner_proof': {
        'session': 'u32',
        'trie_nodes': ['Bytes'],
        'validator_count': 'u32',
    },
}
)

Storage functions¶

AuthorVrfRandomness¶

This field should always be populated during block processing unless secondary plain slots are enabled (which don't contain a VRF output).

It is set in on_finalize, before it will contain the value from the last block.

Python¶

result = substrate.query(
    'Babe', 'AuthorVrfRandomness', []
)

Return value¶

(None, '[u8; 32]')

Authorities¶

Current epoch authorities.

Python¶

result = substrate.query(
    'Babe', 'Authorities', []
)

Return value¶

[('[u8; 32]', 'u64')]

CurrentSlot¶

Current slot number.

Python¶

result = substrate.query(
    'Babe', 'CurrentSlot', []
)

Return value¶

'u64'

EpochConfig¶

The configuration for the current epoch. Should never be None as it is initialized in genesis.

Python¶

result = substrate.query(
    'Babe', 'EpochConfig', []
)

Return value¶

{
    'allowed_slots': (
        'PrimarySlots',
        'PrimaryAndSecondaryPlainSlots',
        'PrimaryAndSecondaryVRFSlots',
    ),
    'c': ('u64', 'u64'),
}

EpochIndex¶

Current epoch index.

Python¶

result = substrate.query(
    'Babe', 'EpochIndex', []
)

Return value¶

'u64'

EpochStart¶

The block numbers when the last and current epoch have started, respectively N-1 and N. NOTE: We track this is in order to annotate the block number when a given pool of entropy was fixed (i.e. it was known to chain observers). Since epochs are defined in slots, which may be skipped, the block numbers may not line up with the slot numbers.

Python¶

result = substrate.query(
    'Babe', 'EpochStart', []
)

Return value¶

('u32', 'u32')

GenesisSlot¶

The slot at which the first epoch actually started. This is 0 until the first block of the chain.

Python¶

result = substrate.query(
    'Babe', 'GenesisSlot', []
)

Return value¶

'u64'

Initialized¶

Temporary value (cleared at block finalization) which is Some if per-block initialization has already been called for current block.

Python¶

result = substrate.query(
    'Babe', 'Initialized', []
)

Return value¶

(
    None,
    {
        None: None,
        'Primary': {
            'authority_index': 'u32',
            'slot': 'u64',
            'vrf_output': '[u8; 32]',
            'vrf_proof': '[u8; 64]',
        },
        'SecondaryPlain': {'authority_index': 'u32', 'slot': 'u64'},
        'SecondaryVRF': {
            'authority_index': 'u32',
            'slot': 'u64',
            'vrf_output': '[u8; 32]',
            'vrf_proof': '[u8; 64]',
        },
    },
)

Lateness¶

How late the current block is compared to its parent.

This entry is populated as part of block execution and is cleaned up on block finalization. Querying this storage entry outside of block execution context should always yield zero.

Python¶

result = substrate.query(
    'Babe', 'Lateness', []
)

Return value¶

'u32'

NextAuthorities¶

Next epoch authorities.

Python¶

result = substrate.query(
    'Babe', 'NextAuthorities', []
)

Return value¶

[('[u8; 32]', 'u64')]

NextEpochConfig¶

The configuration for the next epoch, None if the config will not change (you can fallback to EpochConfig instead in that case).

Python¶

result = substrate.query(
    'Babe', 'NextEpochConfig', []
)

Return value¶

{
    'allowed_slots': (
        'PrimarySlots',
        'PrimaryAndSecondaryPlainSlots',
        'PrimaryAndSecondaryVRFSlots',
    ),
    'c': ('u64', 'u64'),
}

NextRandomness¶

Next epoch randomness.

Python¶

result = substrate.query(
    'Babe', 'NextRandomness', []
)

Return value¶

'[u8; 32]'

PendingEpochConfigChange¶

Pending epoch configuration change that will be applied when the next epoch is enacted.

Python¶

result = substrate.query(
    'Babe', 'PendingEpochConfigChange', []
)

Return value¶

{
    None: None,
    'V1': {
        'allowed_slots': (
            'PrimarySlots',
            'PrimaryAndSecondaryPlainSlots',
            'PrimaryAndSecondaryVRFSlots',
        ),
        'c': ('u64', 'u64'),
    },
}

Randomness¶

The epoch randomness for the current epoch.

# Security

This MUST NOT be used for gambling, as it can be influenced by a malicious validator in the short term. It MAY be used in many cryptographic protocols, however, so long as one remembers that this (like everything else on-chain) it is public. For example, it can be used where a number is needed that cannot have been chosen by an adversary, for purposes such as public-coin zero-knowledge proofs.

Python¶

result = substrate.query(
    'Babe', 'Randomness', []
)

Return value¶

'[u8; 32]'

SegmentIndex¶

Randomness under construction.

We make a trade-off between storage accesses and list length. We store the under-construction randomness in segments of up to UNDER_CONSTRUCTION_SEGMENT_LENGTH.

Once a segment reaches this length, we begin the next one. We reset all segments and return to 0 at the beginning of every epoch.

Python¶

result = substrate.query(
    'Babe', 'SegmentIndex', []
)

Return value¶

'u32'

SkippedEpochs¶

A list of the last 100 skipped epochs and the corresponding session index when the epoch was skipped.

This is only used for validating equivocation proofs. An equivocation proof must contains a key-ownership proof for a given session, therefore we need a way to tie together sessions and epoch indices, i.e. we need to validate that a validator was the owner of a given key on a given session, and what the active epoch index was during that session.

Python¶

result = substrate.query(
    'Babe', 'SkippedEpochs', []
)

Return value¶

[('u64', 'u32')]

UnderConstruction¶

TWOX-NOTE: SegmentIndex is an increasing integer, so this is okay.

Python¶

result = substrate.query(
    'Babe', 'UnderConstruction', ['u32']
)

Return value¶

['[u8; 32]']

Constants¶

EpochDuration¶

The amount of time, in slots, that each epoch should last. NOTE: Currently it is not possible to change the epoch duration after the chain has started. Attempting to do so will brick block production.

Value¶

Python¶

constant = substrate.get_constant('Babe', 'EpochDuration')

ExpectedBlockTime¶

The expected average block time at which BABE should be creating blocks. Since BABE is probabilistic it is not trivial to figure out what the expected average block time should be based on the slot duration and the security parameter c (where 1 - c represents the probability of a slot being empty).

Value¶

Python¶

constant = substrate.get_constant('Babe', 'ExpectedBlockTime')

MaxAuthorities¶

Max number of authorities allowed

Value¶

Python¶

constant = substrate.get_constant('Babe', 'MaxAuthorities')

Errors¶

DuplicateOffenceReport¶

A given equivocation report is valid but already previously reported.

InvalidConfiguration¶

Submitted configuration is invalid.

InvalidEquivocationProof¶

An equivocation proof provided as part of an equivocation report is invalid.

InvalidKeyOwnershipProof¶

A key ownership proof provided as part of an equivocation report is invalid.