Merge pull request #1834 from ethereum/clarify-genesis-safety

clarify that eth1 block follow distance for genesis
ethereum · May 20, 2020 · a6d4566 · a6d4566
2 parents 7cb8e5e + 4ac2fc7
commit a6d4566
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diff --git a/specs/phase0/beacon-chain.md b/specs/phase0/beacon-chain.md
@@ -183,6 +183,7 @@ The following values are (non-configurable) constants used throughout the specif
 
 | Name | Value |
 | - | - |
+| `ETH1_FOLLOW_DISTANCE` | `2**10` (= 1,024) |
 | `MAX_COMMITTEES_PER_SLOT` | `2**6` (= 64) |
 | `TARGET_COMMITTEE_SIZE` | `2**7` (= 128) |
 | `MAX_VALIDATORS_PER_COMMITTEE` | `2**11` (= 2,048) |
@@ -219,6 +220,7 @@ The following values are (non-configurable) constants used throughout the specif
 | - | - | :-: | :-: |
 | `MIN_GENESIS_DELAY` | `86400` | seconds | 1 day |
 | `SECONDS_PER_SLOT` | `12` | seconds | 12 seconds |
+| `SECONDS_PER_ETH1_BLOCK` | `14` | seconds | 14 seconds |
 | `MIN_ATTESTATION_INCLUSION_DELAY` | `2**0` (= 1) | slots | 12 seconds |
 | `SLOTS_PER_EPOCH` | `2**5` (= 32) | slots | 6.4 minutes |
 | `MIN_SEED_LOOKAHEAD` | `2**0` (= 1) | epochs | 6.4 minutes |
@@ -229,7 +231,6 @@ The following values are (non-configurable) constants used throughout the specif
 | `MIN_VALIDATOR_WITHDRAWABILITY_DELAY` | `2**8` (= 256) | epochs | ~27 hours |
 | `SHARD_COMMITTEE_PERIOD` | `Epoch(2**8)` (= 256) | epochs | ~27 hours |
 
-
 ### State list lengths
 
 | Name | Value | Unit | Duration |
@@ -1136,6 +1137,8 @@ Before the Ethereum 2.0 genesis has been triggered, and for every Ethereum 1.0 b
 - `eth1_timestamp` is the Unix timestamp corresponding to `eth1_block_hash`
 - `deposits` is the sequence of all deposits, ordered chronologically, up to (and including) the block with hash `eth1_block_hash`
 
+Eth1 blocks must only be considered once they are at least `SECONDS_PER_ETH1_BLOCK * ETH1_FOLLOW_DISTANCE` seconds old (i.e. `eth1_timestamp + SECONDS_PER_ETH1_BLOCK * ETH1_FOLLOW_DISTANCE <= current_unix_time`). Due to this constraint, if `MIN_GENESIS_DELAY < SECONDS_PER_ETH1_BLOCK * ETH1_FOLLOW_DISTANCE`, then the `genesis_time` can happen before the time/state is first known. Values should be configured to avoid this case.
+
 ```python
 def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
                                       eth1_timestamp: uint64,

diff --git a/specs/phase0/validator.md b/specs/phase0/validator.md
@@ -85,11 +85,9 @@ All terminology, constants, functions, and protocol mechanics defined in the [Ph
 
 | Name | Value | Unit | Duration |
 | - | - | :-: | :-: |
-| `ETH1_FOLLOW_DISTANCE` | `2**10` (= 1,024) | blocks | ~4 hours |
 | `TARGET_AGGREGATORS_PER_COMMITTEE` | `2**4` (= 16) | validators | |
 | `RANDOM_SUBNETS_PER_VALIDATOR` | `2**0` (= 1) | subnets | |
 | `EPOCHS_PER_RANDOM_SUBNET_SUBSCRIPTION` | `2**8` (= 256) | epochs | ~27 hours |
-| `SECONDS_PER_ETH1_BLOCK` | `14` | seconds | |
 | `ATTESTATION_SUBNET_COUNT` | `64` | The number of attestation subnets used in the gossipsub protocol. |
 
 ## Becoming a validator