diff --git a/configs/mainnet.yaml b/configs/mainnet.yaml
index 6eb5641d0..74f062d9b 100644
--- a/configs/mainnet.yaml
+++ b/configs/mainnet.yaml
@@ -143,6 +143,8 @@ DOMAIN_BEACON_ATTESTER: 0x01000000
 DOMAIN_RANDAO: 0x02000000
 DOMAIN_DEPOSIT: 0x03000000
 DOMAIN_VOLUNTARY_EXIT: 0x04000000
+DOMAIN_SELECTION_PROOF: 0x05000000
+DOMAIN_AGGREGATE_AND_PROOF: 0x06000000
 # Phase 1
 DOMAIN_SHARD_PROPOSAL: 0x80000000
 DOMAIN_SHARD_COMMITTEE: 0x81000000
diff --git a/configs/minimal.yaml b/configs/minimal.yaml
index 03ffa90e3..42c63e301 100644
--- a/configs/minimal.yaml
+++ b/configs/minimal.yaml
@@ -142,6 +142,8 @@ DOMAIN_BEACON_ATTESTER: 0x01000000
 DOMAIN_RANDAO: 0x02000000
 DOMAIN_DEPOSIT: 0x03000000
 DOMAIN_VOLUNTARY_EXIT: 0x04000000
+DOMAIN_SELECTION_PROOF: 0x05000000
+DOMAIN_AGGREGATE_AND_PROOF: 0x06000000
 # Phase 1
 DOMAIN_SHARD_PROPOSAL: 0x80000000
 DOMAIN_SHARD_COMMITTEE: 0x81000000
diff --git a/specs/phase0/beacon-chain.md b/specs/phase0/beacon-chain.md
index 96ea351c8..2ab51079d 100644
--- a/specs/phase0/beacon-chain.md
+++ b/specs/phase0/beacon-chain.md
@@ -253,11 +253,14 @@ The following values are (non-configurable) constants used throughout the specif
 
 | Name | Value |
 | - | - |
-| `DOMAIN_BEACON_PROPOSER` | `DomainType('0x00000000')` |
-| `DOMAIN_BEACON_ATTESTER` | `DomainType('0x01000000')` |
-| `DOMAIN_RANDAO` | `DomainType('0x02000000')` |
-| `DOMAIN_DEPOSIT` | `DomainType('0x03000000')` |
-| `DOMAIN_VOLUNTARY_EXIT` | `DomainType('0x04000000')` |
+| `DOMAIN_BEACON_PROPOSER`     | `DomainType('0x00000000')` |
+| `DOMAIN_BEACON_ATTESTER`     | `DomainType('0x01000000')` |
+| `DOMAIN_RANDAO`              | `DomainType('0x02000000')` |
+| `DOMAIN_DEPOSIT`             | `DomainType('0x03000000')` |
+| `DOMAIN_VOLUNTARY_EXIT`      | `DomainType('0x04000000')` |
+| `DOMAIN_SELECTION_PROOF`     | `DomainType('0x05000000')` |
+| `DOMAIN_AGGREGATE_AND_PROOF` | `DomainType('0x06000000')` |
+
 
 ## Containers
 
diff --git a/specs/phase0/validator.md b/specs/phase0/validator.md
index 3b9e85d16..9229a34f4 100644
--- a/specs/phase0/validator.md
+++ b/specs/phase0/validator.md
@@ -424,7 +424,7 @@ A validator is selected to aggregate based upon the return value of `is_aggregat
 
 ```python
 def get_slot_signature(state: BeaconState, slot: Slot, privkey: int) -> BLSSignature:
-    domain = get_domain(state, DOMAIN_BEACON_ATTESTER, compute_epoch_at_slot(slot))
+    domain = get_domain(state, DOMAIN_SELECTION_PROOF, compute_epoch_at_slot(slot))
     signing_root = compute_signing_root(slot, domain)
     return bls.Sign(privkey, signing_root)
 ```
@@ -468,6 +468,32 @@ Selection proofs are provided in `AggregateAndProof` to prove to the gossip chan
 
 `AggregateAndProof` messages are signed by the aggregator and broadcast inside of `SignedAggregateAndProof` objects to prevent a class of DoS attacks and message forgeries.
 
+First, `aggregate_and_proof = get_aggregate_and_proof(state, aggregate_attestation, validator_index, privkey)` is contructed.
+
+```python
+def get_aggregate_and_proof(state: BeaconState,
+                            aggregate: Attestation,
+                            aggregator_index: ValidatorIndex,
+                            privkey: int) -> AggregateAndProof:
+    return AggregateAndProof(
+        aggregator_index=aggregator_index,
+        aggregate=aggregate,
+        selection_proof=get_slot_signature(state, aggregate.data.slot, privkey),
+    )
+```
+
+Then `signed_aggregate_and_proof = SignedAggregateAndProof(message=aggregate_and_proof, signature=signature)` is constructed and broadast. Where `signature` is obtained from:
+
+```python
+def get_aggregate_and_proof_signature(state: BeaconState,
+                                      aggregate_and_proof: AggregateAndProof,
+                                      privkey: int) -> BLSSignature:
+    aggregate = aggregate_and_proof.aggregate
+    domain = get_domain(state, DOMAIN_AGGREGATE_AND_PROOF, compute_epoch_at_slot(aggregate.data.slot))
+    signing_root = compute_signing_root(aggregate_and_proof, domain)
+    return bls.Sign(privkey, signing_root)
+```
+
 ##### `AggregateAndProof`
 
 ```python