Merge pull request #1221 from ethereum/ralexstokes-patch-3

Clarify `get_randao_mix` accessor
ethereum · Jun 29, 2019 · aec9719 · aec9719
2 parents 34ad123 + 2a2bd72
commit aec9719
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
@@ -786,7 +786,7 @@ def generate_seed(state: BeaconState,
     Generate a seed for the given ``epoch``.
     """
     return hash(
-        get_randao_mix(state, Epoch(epoch + EPOCHS_PER_HISTORICAL_VECTOR - MIN_SEED_LOOKAHEAD)) +
+        get_randao_mix(state, Epoch(epoch + EPOCHS_PER_HISTORICAL_VECTOR - MIN_SEED_LOOKAHEAD)) +  # Avoid underflow
         hash_tree_root(List[ValidatorIndex, VALIDATOR_REGISTRY_LIMIT](get_active_validator_indices(state, epoch))) +
         int_to_bytes(epoch, length=32)
     )