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Modify long-lived attestation subnet calculation to allow pre-determined calculation #3545

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Modify long-lived attestation subnet calculation to allow pre-determined calculation #3545

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0a86ab4
Introduce a shuffling prefix for subnet determination
AgeManning Nov 7, 2023
ec9fbf2
Split the bits in the calculation to clarify the logic
AgeManning Nov 8, 2023
22def22
Update specs/phase0/p2p-interface.md
AgeManning Nov 30, 2023
48e685c
Update config files
hwwhww Jan 9, 2024
2fe8346
Add temporary values for lint
AgeManning Jan 15, 2024
1ec248a
Fix lint
hwwhww Jan 15, 2024
050a946
Merge latest dev
AgeManning Mar 14, 2024
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1 change: 1 addition & 0 deletions configs/mainnet.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -138,6 +138,7 @@ ATTESTATION_SUBNET_COUNT: 64
ATTESTATION_SUBNET_EXTRA_BITS: 0
# ceillog2(ATTESTATION_SUBNET_COUNT) + ATTESTATION_SUBNET_EXTRA_BITS
ATTESTATION_SUBNET_PREFIX_BITS: 6
ATTESTATION_SUBNET_SHUFFLING_PREFIX_BITS: 3

# Deneb
# `2**7` (=128)
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1 change: 1 addition & 0 deletions configs/minimal.yaml
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Expand Up @@ -139,6 +139,7 @@ ATTESTATION_SUBNET_COUNT: 64
ATTESTATION_SUBNET_EXTRA_BITS: 0
# ceillog2(ATTESTATION_SUBNET_COUNT) + ATTESTATION_SUBNET_EXTRA_BITS
ATTESTATION_SUBNET_PREFIX_BITS: 6
ATTESTATION_SUBNET_SHUFFLING_PREFIX_BITS: 3

# Deneb
# `2**7` (=128)
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22 changes: 16 additions & 6 deletions specs/phase0/p2p-interface.md
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Expand Up @@ -202,8 +202,9 @@ This section outlines configurations that are used in this spec.
| `MESSAGE_DOMAIN_VALID_SNAPPY` | `DomainType('0x01000000')` | 4-byte domain for gossip message-id isolation of *valid* snappy messages |
| `SUBNETS_PER_NODE` | `2` | The number of long-lived subnets a beacon node should be subscribed to. |
| `ATTESTATION_SUBNET_COUNT` | `2**6` (= 64) | The number of attestation subnets used in the gossipsub protocol. |
| `ATTESTATION_SUBNET_EXTRA_BITS` | `0` | The number of extra bits of a NodeId to use when mapping to a subscribed subnet |
| `ATTESTATION_SUBNET_PREFIX_BITS` | `int(ceillog2(ATTESTATION_SUBNET_COUNT) + ATTESTATION_SUBNET_EXTRA_BITS)` | |
| `ATTESTATION_SUBNET_EXTRA_BITS` | `0` | The number of extra bits of a NodeId to use when mapping to a subscribed subnet | |
| `ATTESTATION_SUBNET_PREFIX_BITS` | `int(ceillog2(ATTESTATION_SUBNET_COUNT) + ATTESTATION_SUBNET_EXTRA_BITS)` |
| `ATTESTATION_SUBNET_SHUFFLING_PREFIX_BITS` | `3` | The number of bits used to shuffle nodes to a new subnet within `EPOCHS_PER_SUBNET_SUBSCRIPTION` | |
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### MetaData

Expand Down Expand Up @@ -1020,11 +1021,20 @@ Because Phase 0 does not have shards and thus does not have Shard Committees, th

```python
def compute_subscribed_subnet(node_id: NodeID, epoch: Epoch, index: int) -> SubnetID:
node_id_prefix = node_id >> (NODE_ID_BITS - ATTESTATION_SUBNET_PREFIX_BITS)
node_offset = node_id % EPOCHS_PER_SUBNET_SUBSCRIPTION
permutation_seed = hash(uint_to_bytes(uint64((epoch + node_offset) // EPOCHS_PER_SUBNET_SUBSCRIPTION)))
subnet_prefix = node_id >> (NODE_ID_BITS - ATTESTATION_SUBNET_PREFIX_BITS)
shuffling_bit_size = (
NODE_ID_BITS
- ATTESTATION_SUBNET_PREFIX_BITS
- ATTESTATION_SUBNET_SHUFFLING_PREFIX_BITS
)
shuffling_bits = (node_id >> shuffling_bit_size) % (1 << ATTESTATION_SUBNET_SHUFFLING_PREFIX_BITS)
shuffling_multiplier = EPOCHS_PER_SUBNET_SUBSCRIPTION >> ATTESTATION_SUBNET_SHUFFLING_PREFIX_BITS
epoch_transition = (
(subnet_prefix + (shuffling_bits * shuffling_multiplier)) % EPOCHS_PER_SUBNET_SUBSCRIPTION
)
permutation_seed = hash(uint_to_bytes(uint64((epoch + epoch_transition) // EPOCHS_PER_SUBNET_SUBSCRIPTION)))
permutated_prefix = compute_shuffled_index(
node_id_prefix,
subnet_prefix,
1 << ATTESTATION_SUBNET_PREFIX_BITS,
permutation_seed,
)
Expand Down