diff --git a/Makefile b/Makefile
index e8f3d21bc..8cd7daf58 100644
--- a/Makefile
+++ b/Makefile
@@ -71,7 +71,7 @@ pyspec:
 
 # installs the packages to run pyspec tests
 install_test:
-	python3 -m venv venv; . venv/bin/activate; pip3 install .[test] .[lint]
+	python3.8 -m venv venv; . venv/bin/activate; pip3 install .[lint]; pip3 install -e .[test]
 
 test: pyspec
 	. venv/bin/activate; cd $(PY_SPEC_DIR); \
diff --git a/configs/minimal.yaml b/configs/minimal.yaml
index 9daf428b4..256c2b3fa 100644
--- a/configs/minimal.yaml
+++ b/configs/minimal.yaml
@@ -205,9 +205,9 @@ RANDAO_PENALTY_EPOCHS: 2
 # [customized] quicker for testing
 EARLY_DERIVED_SECRET_PENALTY_MAX_FUTURE_EPOCHS: 4096
 # 2**11 (= 2,048) epochs
-EPOCHS_PER_CUSTODY_PERIOD: 2048
+EPOCHS_PER_CUSTODY_PERIOD: 8
 # 2**11 (= 2,048) epochs
-CUSTODY_PERIOD_TO_RANDAO_PADDING: 2048
+CUSTODY_PERIOD_TO_RANDAO_PADDING: 8
 # 2**7 (= 128) epochs
 MAX_REVEAL_LATENESS_DECREMENT: 128
 
diff --git a/setup.py b/setup.py
index 911eb65b0..91c29a6cc 100644
--- a/setup.py
+++ b/setup.py
@@ -121,7 +121,7 @@ from lru import LRU
 from eth2spec.utils.ssz.ssz_impl import hash_tree_root
 from eth2spec.utils.ssz.ssz_typing import (
     View, boolean, Container, List, Vector, uint64, uint8, bit,
-    ByteList, Bytes1, Bytes4, Bytes32, Bytes48, Bytes96, Bitlist, Bitvector,
+    ByteList, ByteVector, Bytes1, Bytes4, Bytes32, Bytes48, Bytes96, Bitlist, Bitvector,
 )
 from eth2spec.utils import bls
 
diff --git a/specs/phase1/beacon-chain.md b/specs/phase1/beacon-chain.md
index 596b3818f..18c5f347f 100644
--- a/specs/phase1/beacon-chain.md
+++ b/specs/phase1/beacon-chain.md
@@ -109,6 +109,99 @@ Configuration is not namespaced. Instead it is strictly an extension;
 | `DOMAIN_SHARD_PROPOSAL` | `DomainType('0x80000000')` | |
 | `DOMAIN_SHARD_COMMITTEE` | `DomainType('0x81000000')` | |
 | `DOMAIN_LIGHT_CLIENT` | `DomainType('0x82000000')` | |
+| `MAX_CUSTODY_CHUNK_CHALLENGE_RECORDS` | `2**20` (= 1,048,576) |
+| `BYTES_PER_CUSTODY_CHUNK` | `2**12` | bytes |
+| `MAX_CUSTODY_RESPONSE_DEPTH` | `ceillog2(MAX_SHARD_BLOCK_SIZE // BYTES_PER_CUSTODY_CHUNK) | - | - |
+
+
+
+## New containers
+
+### `CustodyChunkChallenge`
+
+```python
+class CustodyChunkChallenge(Container):
+    responder_index: ValidatorIndex
+    shard_transition: ShardTransition
+    attestation: Attestation
+    data_index: uint64
+    chunk_index: uint64
+```
+
+### `CustodyChunkChallengeRecord`
+
+```python
+class CustodyChunkChallengeRecord(Container):
+    challenge_index: uint64
+    challenger_index: ValidatorIndex
+    responder_index: ValidatorIndex
+    inclusion_epoch: Epoch
+    data_root: Root
+    depth: uint64
+    chunk_index: uint64
+```
+
+#### `CustodyChunkResponse`
+
+```python
+class CustodyChunkResponse(Container):
+    challenge_index: uint64
+    chunk_index: uint64
+    chunk: ByteVector[BYTES_PER_CUSTODY_CHUNK]
+    branch: List[Root, MAX_CUSTODY_RESPONSE_DEPTH]
+```
+
+#### `CustodySlashing`
+
+```python
+class CustodySlashing(Container):
+    # Attestation.custody_bits_blocks[data_index][committee.index(malefactor_index)] is the target custody bit to check.
+    # (Attestation.data.shard_transition_root as ShardTransition).shard_data_roots[data_index] is the root of the data.
+    data_index: uint64
+    malefactor_index: ValidatorIndex
+    malefactor_secret: BLSSignature
+    whistleblower_index: ValidatorIndex
+    shard_transition: ShardTransition
+    attestation: Attestation
+    data: ByteList[MAX_SHARD_BLOCK_SIZE]
+```
+
+#### `SignedCustodySlashing`
+
+```python
+class SignedCustodySlashing(Container):
+    message: CustodySlashing
+    signature: BLSSignature
+```
+
+
+#### `CustodyKeyReveal`
+
+```python
+class CustodyKeyReveal(Container):
+    # Index of the validator whose key is being revealed
+    revealer_index: ValidatorIndex
+    # Reveal (masked signature)
+    reveal: BLSSignature
+```
+
+#### `EarlyDerivedSecretReveal`
+
+Represents an early (punishable) reveal of one of the derived secrets, where derived secrets are RANDAO reveals and custody reveals (both are part of the same domain).
+
+```python
+class EarlyDerivedSecretReveal(Container):
+    # Index of the validator whose key is being revealed
+    revealed_index: ValidatorIndex
+    # RANDAO epoch of the key that is being revealed
+    epoch: Epoch
+    # Reveal (masked signature)
+    reveal: BLSSignature
+    # Index of the validator who revealed (whistleblower)
+    masker_index: ValidatorIndex
+    # Mask used to hide the actual reveal signature (prevent reveal from being stolen)
+    mask: Bytes32
+```
 
 ## Updated containers
 
@@ -285,6 +378,8 @@ class BeaconState(Container):
     # at RANDAO reveal period % EARLY_DERIVED_SECRET_PENALTY_MAX_FUTURE_EPOCHS
     exposed_derived_secrets: Vector[List[ValidatorIndex, MAX_EARLY_DERIVED_SECRET_REVEALS * SLOTS_PER_EPOCH],
                                     EARLY_DERIVED_SECRET_PENALTY_MAX_FUTURE_EPOCHS]
+    custody_chunk_challenge_records: List[CustodyChunkChallengeRecord, MAX_CUSTODY_CHUNK_CHALLENGE_RECORDS]
+    custody_chunk_challenge_index: uint64
 ```
 
 ## New containers
diff --git a/specs/phase1/custody-game.md b/specs/phase1/custody-game.md
index 6315955f5..f069c4cd2 100644
--- a/specs/phase1/custody-game.md
+++ b/specs/phase1/custody-game.md
@@ -65,6 +65,9 @@ This document details the beacon chain additions and changes in Phase 1 of Ether
 | `EPOCHS_PER_CUSTODY_PERIOD` | `2**11` (= 2,048) | epochs | ~9 days |
 | `CUSTODY_PERIOD_TO_RANDAO_PADDING` | `2**11` (= 2,048) | epochs | ~9 days |
 | `MAX_REVEAL_LATENESS_DECREMENT` | `2**7` (= 128) | epochs | ~14 hours |
+| `CHUNK_RESPONSE_DEADLINE` | `2**14` (= 16,384) | epochs | ~73 days |
+| `MAX_CHUNK_CHALLENGE_DELAY` | `2**11` (= 16,384) | epochs | ~9 days |
+| `CUSTODY_RESPONSE_DEADLINE` | `2**14` (= 16,384) | epochs | ~73 days |
 
 ### Max operations per block
 
@@ -72,6 +75,7 @@ This document details the beacon chain additions and changes in Phase 1 of Ether
 | - | - |
 | `MAX_CUSTODY_KEY_REVEALS` | `2**8` (= 256) |
 | `MAX_EARLY_DERIVED_SECRET_REVEALS` | `1` |
+| `MAX_CUSTODY_CHUNK_CHALLENGES` | `2**2` (= 4) |
 | `MAX_CUSTODY_SLASHINGS` | `1` |
 
 ### Reward and penalty quotients
@@ -93,61 +97,20 @@ The following types are defined, mapping into `DomainType` (little endian):
 
 ### New Beacon Chain operations
 
-#### `CustodySlashing`
-
-```python
-class CustodySlashing(Container):
-    # Attestation.custody_bits_blocks[data_index][committee.index(malefactor_index)] is the target custody bit to check.
-    # (Attestation.data.shard_transition_root as ShardTransition).shard_data_roots[data_index] is the root of the data.
-    data_index: uint64
-    malefactor_index: ValidatorIndex
-    malefactor_secret: BLSSignature
-    whistleblower_index: ValidatorIndex
-    shard_transition: ShardTransition
-    attestation: Attestation
-    data: ByteList[MAX_SHARD_BLOCK_SIZE]
-```
-
-#### `SignedCustodySlashing`
-
-```python
-class SignedCustodySlashing(Container):
-    message: CustodySlashing
-    signature: BLSSignature
-```
-
-
-#### `CustodyKeyReveal`
-
-```python
-class CustodyKeyReveal(Container):
-    # Index of the validator whose key is being revealed
-    revealer_index: ValidatorIndex
-    # Reveal (masked signature)
-    reveal: BLSSignature
-```
-
-#### `EarlyDerivedSecretReveal`
-
-Represents an early (punishable) reveal of one of the derived secrets, where derived secrets are RANDAO reveals and custody reveals (both are part of the same domain).
-
-```python
-class EarlyDerivedSecretReveal(Container):
-    # Index of the validator whose key is being revealed
-    revealed_index: ValidatorIndex
-    # RANDAO epoch of the key that is being revealed
-    epoch: Epoch
-    # Reveal (masked signature)
-    reveal: BLSSignature
-    # Index of the validator who revealed (whistleblower)
-    masker_index: ValidatorIndex
-    # Mask used to hide the actual reveal signature (prevent reveal from being stolen)
-    mask: Bytes32
-```
-
-
 ## Helpers
 
+### `replace_empty_or_append`
+
+```python
+def replace_empty_or_append(list: List, new_element: Any) -> int:
+    for i in range(len(list)):
+        if list[i] == empty(typeof(new_element)):
+            list[i] = new_element
+            return i
+    list.append(new_element)
+    return len(list) - 1
+```
+
 ### `legendre_bit`
 
 Returns the Legendre symbol `(a/q)` normalizes as a bit (i.e. `((a/q) + 1) // 2`). In a production implementation, a well-optimized library (e.g. GMP) should be used for this.
@@ -248,6 +211,84 @@ def process_custody_game_operations(state: BeaconState, body: BeaconBlockBody) -
     for_ops(body.custody_slashings, process_custody_slashing)
 ```
 
+#### Chunk challenges
+
+Verify that `len(block.body.custody_chunk_challenges) <= MAX_CUSTODY_CHUNK_CHALLENGES`.
+
+For each `challenge` in `block.body.custody_chunk_challenges`, run the following function:
+
+```python
+def process_chunk_challenge(state: BeaconState, challenge: CustodyChunkChallenge) -> None:
+    # Verify the attestation
+    assert is_valid_indexed_attestation(state, get_indexed_attestation(state, challenge.attestation))
+    # Verify it is not too late to challenge
+    assert (challenge.attestation.data.target.epoch + MAX_CHUNK_CHALLENGE_DELAY
+            >= get_current_epoch(state))
+    responder = state.validators[challenge.responder_index]
+    assert (responder.exit_epoch == FAR_FUTURE_EPOCH 
+            or responder.exit_epoch + MAX_CHUNK_CHALLENGE_DELAY >= get_current_epoch(state))
+    # Verify responder is slashable
+    assert is_slashable_validator(responder, get_current_epoch(state))
+    # Verify the responder participated in the attestation
+    attesters = get_attesting_indices(state, challenge.attestation.data, challenge.attestation.aggregation_bits)
+    assert challenge.responder_index in attesters
+    # Verify shard transition is correctly given
+    assert hash_tree_root(challenge.shard_transition) == challenge.attestation.data.shard_transition_root
+    data_root = challenge.shard_transition.shard_data_roots[challenge.data_index]
+    # Verify the challenge is not a duplicate
+    for record in state.custody_chunk_challenge_records:
+        assert (
+            record.data_root != challenge.attestation.data.crosslink.data_root or
+            record.chunk_index != challenge.chunk_index
+        )
+    # Verify depth
+    transition_chunks = (challenge.shard_transition.shard_block_lengths[challenge.data_index] + BYTES_PER_CUSTODY_CHUNK - 1) // BYTES_PER_CUSTODY_CHUNK
+    depth = ceillog2(transition_chunks)
+    assert challenge.chunk_index < transition_chunks
+    # Add new chunk challenge record
+    new_record = CustodyChunkChallengeRecord(
+        challenge_index=state.custody_chunk_challenge_index,
+        challenger_index=get_beacon_proposer_index(state),
+        responder_index=challenge.responder_index,
+        inclusion_epoch=get_current_epoch(state),
+        data_root=challenge.shard_transition.shard_data_roots[challenge.data_index],
+        depth=depth,
+        chunk_index=challenge.chunk_index,
+    )
+    replace_empty_or_append(state.custody_chunk_challenge_records, new_record)
+
+    state.custody_chunk_challenge_index += 1
+    # Postpone responder withdrawability
+    responder.withdrawable_epoch = FAR_FUTURE_EPOCH
+```
+
+#### Custody chunk response
+
+```python
+def process_chunk_challenge_response(state: BeaconState,
+                                     response: CustodyChunkResponse) -> None:
+
+    challenge = next((record for record in state.custody_chunk_challenge_records if record.challenge_index == response.challenge_index), None)
+    assert(challenge is not None)
+
+    # Verify chunk index
+    assert response.chunk_index == challenge.chunk_index
+    # Verify the chunk matches the crosslink data root
+    assert is_valid_merkle_branch(
+        leaf=hash_tree_root(response.chunk),
+        branch=response.branch,
+        depth=challenge.depth,
+        index=response.chunk_index,
+        root=challenge.data_root,
+    )
+    # Clear the challenge
+    records = state.custody_chunk_challenge_records
+    records[records.index(challenge)] = CustodyChunkChallengeRecord()
+    # Reward the proposer
+    proposer_index = get_beacon_proposer_index(state)
+    increase_balance(state, proposer_index, get_base_reward(state, proposer_index) // MINOR_REWARD_QUOTIENT)
+```
+
 #### Custody key reveals
 
 ```python
@@ -431,14 +472,22 @@ Run `process_reveal_deadlines(state)` after `process_registry_updates(state)`:
 def process_reveal_deadlines(state: BeaconState) -> None:
     epoch = get_current_epoch(state)
     for index, validator in enumerate(state.validators):
-        if get_custody_period_for_validator(ValidatorIndex(index), epoch) > validator.next_custody_secret_to_reveal:
-            # ------------------  WARNING  ----------------------- #
-            # UNSAFE REMOVAL OF SLASHING TO PRIORITIZE PHASE 0 CI  #
-            # Must find generic way to handle key reveals in tests #
-            # ---------------------------------------------------- #
+        if get_custody_period_for_validator(ValidatorIndex(index), epoch) > validator.next_custody_secret_to_reveal + (CUSTODY_RESPONSE_DEADLINE // EPOCHS_PER_CUSTODY_PERIOD):
+            slash_validator(state, ValidatorIndex(index))
+```
 
-            # slash_validator(state, ValidatorIndex(index))
-            pass
+Run `process_challenge_deadlines(state)` immediately after `process_reveal_deadlines(state)`:
+
+```python
+# begin insert @process_challenge_deadlines
+    process_challenge_deadlines(state)
+# end insert @process_challenge_deadlines
+def process_challenge_deadlines(state: BeaconState) -> None:
+    for custody_chunk_challenge in state.custody_chunk_challenge_records:
+        if get_current_epoch(state) > custody_chunk_challenge.inclusion_epoch + CUSTODY_RESPONSE_DEADLINE:
+            slash_validator(state, custody_chunk_challenge.responder_index, custody_chunk_challenge.challenger_index)
+            records = state.custody_chunk_challenge_records
+            records[records.index(custody_chunk_challenge)] = CustodyChunkChallengeRecord()
 ```
 
 ### Final updates
diff --git a/tests/core/pyspec/eth2spec/test/helpers/attestations.py b/tests/core/pyspec/eth2spec/test/helpers/attestations.py
index 8215f5c5b..325fee260 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/attestations.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/attestations.py
@@ -43,7 +43,7 @@ def run_attestation_processing(spec, state, attestation, valid=True):
     yield 'post', state
 
 
-def build_attestation_data(spec, state, slot, index):
+def build_attestation_data(spec, state, slot, index, shard_transition_root=None):
     assert state.slot >= slot
 
     if slot == state.slot:
@@ -72,6 +72,7 @@ def build_attestation_data(spec, state, slot, index):
         beacon_block_root=block_root,
         source=spec.Checkpoint(epoch=source_epoch, root=source_root),
         target=spec.Checkpoint(epoch=spec.compute_epoch_at_slot(slot), root=epoch_boundary_root),
+        shard_transition_root=shard_transition_root,
     )
 
 
@@ -89,7 +90,7 @@ def convert_to_valid_on_time_attestation(spec, state, attestation, signed=False)
     return attestation
 
 
-def get_valid_on_time_attestation(spec, state, slot=None, index=None, signed=False):
+def get_valid_on_time_attestation(spec, state, slot=None, index=None, signed=False, shard_transition_root=None):
     '''
     Construct on-time attestation for next slot
     '''
@@ -98,10 +99,10 @@ def get_valid_on_time_attestation(spec, state, slot=None, index=None, signed=Fal
     if index is None:
         index = 0
 
-    return get_valid_attestation(spec, state, slot=slot, index=index, signed=signed, on_time=True)
+    return get_valid_attestation(spec, state, slot=slot, index=index, signed=signed, on_time=True, shard_transition_root=shard_transition_root)
 
 
-def get_valid_late_attestation(spec, state, slot=None, index=None, signed=False):
+def get_valid_late_attestation(spec, state, slot=None, index=None, signed=False, shard_transition_root=None):
     '''
     Construct on-time attestation for next slot
     '''
@@ -110,16 +111,16 @@ def get_valid_late_attestation(spec, state, slot=None, index=None, signed=False)
     if index is None:
         index = 0
 
-    return get_valid_attestation(spec, state, slot=slot, index=index, signed=signed, on_time=False)
+    return get_valid_attestation(spec, state, slot=slot, index=index, signed=signed, on_time=False, shard_transition_root=shard_transition_root)
 
 
-def get_valid_attestation(spec, state, slot=None, index=None, empty=False, signed=False, on_time=True):
+def get_valid_attestation(spec, state, slot=None, index=None, empty=False, signed=False, on_time=True, shard_transition_root=None):
     if slot is None:
         slot = state.slot
     if index is None:
         index = 0
 
-    attestation_data = build_attestation_data(spec, state, slot, index)
+    attestation_data = build_attestation_data(spec, state, slot, index, shard_transition_root=shard_transition_root)
 
     beacon_committee = spec.get_beacon_committee(
         state,
diff --git a/tests/core/pyspec/eth2spec/test/helpers/custody.py b/tests/core/pyspec/eth2spec/test/helpers/custody.py
index 7c51675cd..45c29be9a 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/custody.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/custody.py
@@ -1,8 +1,8 @@
 from eth2spec.test.helpers.keys import privkeys
 from eth2spec.utils import bls
-from eth2spec.utils.ssz.ssz_typing import Bitlist, ByteVector, Bitvector
+from eth2spec.utils.ssz.ssz_typing import Bitlist, ByteVector, Bitvector, ByteList
 from eth2spec.utils.ssz.ssz_impl import hash_tree_root
-from eth2spec.utils.merkle_minimal import get_merkle_tree, get_merkle_proof
+from eth2spec.utils.merkle_minimal import get_merkle_root, get_merkle_tree, get_merkle_proof
 from remerkleable.core import pack_bits_to_chunks
 from remerkleable.tree import subtree_fill_to_contents, get_depth
 
@@ -61,7 +61,7 @@ def bitlist_from_int(max_len, num_bits, n):
     return Bitlist[max_len](*[(n >> i) & 0b1 for i in range(num_bits)])
 
 
-def get_valid_bit_challenge(spec, state, attestation, invalid_custody_bit=False):
+def get_valid_custody_slashing(spec, state, attestation, invalid_custody_bit=False):
     beacon_committee = spec.get_beacon_committee(
         state,
         attestation.data.slot,
@@ -96,21 +96,39 @@ def get_valid_bit_challenge(spec, state, attestation, invalid_custody_bit=False)
     )
 
 
+def get_valid_chunk_challenge(spec, state, attestation, shard_transition):
+    shard = spec.compute_shard_from_committee_index(state, attestation.data.index, attestation.data.slot)
+    crosslink_committee = spec.get_beacon_committee(
+        state,
+        attestation.data.slot,
+        attestation.data.index
+    )
+    responder_index = crosslink_committee[0]
+    data_index = len(shard_transition.shard_block_lengths) - 1
+
+    chunk_count = (shard_transition.shard_block_lengths[data_index] + spec.BYTES_PER_CUSTODY_CHUNK - 1) // spec.BYTES_PER_CUSTODY_CHUNK
+
+    return spec.CustodyChunkChallenge(
+        responder_index=responder_index,
+        attestation=attestation,
+        chunk_index=chunk_count - 1,
+        data_index=data_index,
+        shard_transition=shard_transition,
+    )
+
+
 def custody_chunkify(spec, x):
     chunks = [bytes(x[i:i + spec.BYTES_PER_CUSTODY_CHUNK]) for i in range(0, len(x), spec.BYTES_PER_CUSTODY_CHUNK)]
     chunks[-1] = chunks[-1].ljust(spec.BYTES_PER_CUSTODY_CHUNK, b"\0")
     return chunks
 
 
-def get_valid_custody_response(spec, state, bit_challenge, custody_data, challenge_index, invalid_chunk_bit=False):
+def get_valid_custody_chunk_response(spec, state, chunk_challenge, block_length, challenge_index,
+                                     invalid_chunk_data=False):
+    custody_data = get_custody_test_vector(block_length)
     chunks = custody_chunkify(spec, custody_data)
 
-    chunk_index = len(chunks) - 1
-    chunk_bit = spec.get_custody_chunk_bit(bit_challenge.responder_key, chunks[chunk_index])
-
-    while chunk_bit == bit_challenge.chunk_bits[chunk_index] ^ invalid_chunk_bit:
-        chunk_index -= 1
-        chunk_bit = spec.get_custody_chunk_bit(bit_challenge.responder_key, chunks[chunk_index])
+    chunk_index = chunk_challenge.chunk_index
 
     chunks_hash_tree_roots = [hash_tree_root(ByteVector[spec.BYTES_PER_CUSTODY_CHUNK](chunk)) for chunk in chunks]
     chunks_hash_tree_roots += [
@@ -120,31 +138,29 @@ def get_valid_custody_response(spec, state, bit_challenge, custody_data, challen
 
     data_branch = get_merkle_proof(data_tree, chunk_index)
 
-    bitlist_chunk_index = chunk_index // BYTES_PER_CHUNK
-    print(bitlist_chunk_index)
-    bitlist_chunk_nodes = pack_bits_to_chunks(bit_challenge.chunk_bits)
-    bitlist_tree = subtree_fill_to_contents(bitlist_chunk_nodes, get_depth(spec.MAX_CUSTODY_CHUNKS))
-    print(bitlist_tree)
-    bitlist_chunk_branch = None  # TODO; extract proof from merkle tree
-
-    bitlist_chunk_index = chunk_index // 256
-
-    chunk_bits_leaf = Bitvector[256](bit_challenge.chunk_bits[bitlist_chunk_index * 256:
-                                     (bitlist_chunk_index + 1) * 256])
-
-    return spec.CustodyResponse(
+    return spec.CustodyChunkResponse(
         challenge_index=challenge_index,
         chunk_index=chunk_index,
         chunk=ByteVector[spec.BYTES_PER_CUSTODY_CHUNK](chunks[chunk_index]),
-        data_branch=data_branch,
-        chunk_bits_branch=bitlist_chunk_branch,
-        chunk_bits_leaf=chunk_bits_leaf,
+        branch=data_branch,
     )
 
 
 def get_custody_test_vector(bytelength):
-    ints = bytelength // 4
-    return b"".join(i.to_bytes(4, "little") for i in range(ints))
+    ints = bytelength // 4 + 1
+    return (b"".join(i.to_bytes(4, "little") for i in range(ints)))[:bytelength]
+
+
+def get_shard_transition(spec, start_slot, block_lengths):
+    b = [hash_tree_root(ByteVector[x](get_custody_test_vector(x))) for x in block_lengths]
+    shard_transition = spec.ShardTransition(
+        start_slot=start_slot,
+        shard_block_lengths=block_lengths,
+        shard_data_roots=b,
+        shard_states=[spec.Root() for x in block_lengths],
+        proposer_signature_aggregate=spec.BLSSignature(),
+    )
+    return shard_transition
 
 
 def get_custody_merkle_root(data):
diff --git a/tests/core/pyspec/eth2spec/test/helpers/phase1/attestations.py b/tests/core/pyspec/eth2spec/test/helpers/phase1/attestations.py
index 0e16e1fac..061553ef9 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/phase1/attestations.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/phase1/attestations.py
@@ -5,21 +5,23 @@ from eth2spec.test.helpers.keys import privkeys
 import eth2spec.test.helpers.attestations as phase0_attestations
 
 
-def get_valid_on_time_attestation(spec, state, index=None, signed=False):
+def get_valid_on_time_attestation(spec, state, index=None, signed=False, shard_transition_root=None):
     '''
     Construct on-time attestation for next slot
     '''
     if index is None:
         index = 0
 
-    attestation = phase0_attestations.get_valid_attestation(spec, state, state.slot, index, False)
+    attestation = phase0_attestations.get_valid_attestation(spec, state, state.slot, index, False, shard_transition_root=shard_transition_root)
     shard = spec.get_shard(state, attestation)
     offset_slots = spec.compute_offset_slots(spec.get_latest_slot_for_shard(state, shard), state.slot + 1)
+    print(offset_slots)
 
     for _ in offset_slots:
         attestation.custody_bits_blocks.append(
             Bitlist[spec.MAX_VALIDATORS_PER_COMMITTEE]([0 for _ in attestation.aggregation_bits])
         )
+        print(len(attestation.custody_bits_blocks))    
 
     if signed:
         sign_attestation(spec, state, attestation)
diff --git a/tests/core/pyspec/eth2spec/test/phase_1/block_processing/test_process_chunk_challenge.py b/tests/core/pyspec/eth2spec/test/phase_1/block_processing/test_process_chunk_challenge.py
new file mode 100644
index 000000000..09b25a1ad
--- /dev/null
+++ b/tests/core/pyspec/eth2spec/test/phase_1/block_processing/test_process_chunk_challenge.py
@@ -0,0 +1,238 @@
+from eth2spec.test.helpers.custody import (
+    get_valid_chunk_challenge,
+    get_valid_custody_chunk_response,
+    get_custody_test_vector,
+    get_custody_merkle_root,
+    get_shard_transition,
+)
+from eth2spec.test.helpers.attestations import (
+    get_valid_on_time_attestation,
+)
+from eth2spec.test.helpers.state import transition_to
+from eth2spec.utils.ssz.ssz_impl import hash_tree_root
+from eth2spec.test.context import (
+    with_all_phases_except,
+    spec_state_test,
+    expect_assertion_error,
+)
+from eth2spec.test.phase_0.block_processing.test_process_attestation import run_attestation_processing
+
+
+def run_chunk_challenge_processing(spec, state, custody_chunk_challenge, valid=True):
+    """
+    Run ``process_chunk_challenge``, yielding:
+      - pre-state ('pre')
+      - CustodyBitChallenge ('custody_chunk_challenge')
+      - post-state ('post').
+    If ``valid == False``, run expecting ``AssertionError``
+    """
+    yield 'pre', state
+    yield 'custody_chunk_challenge', custody_chunk_challenge
+
+    if not valid:
+        expect_assertion_error(lambda: spec.custody_chunk_challenge(state, custody_chunk_challenge))
+        yield 'post', None
+        return
+
+    spec.process_chunk_challenge(state, custody_chunk_challenge)
+
+    assert state.custody_chunk_challenge_records[state.custody_chunk_challenge_index - 1].responder_index == \
+        custody_chunk_challenge.responder_index
+    assert state.custody_chunk_challenge_records[state.custody_chunk_challenge_index - 1].chunk_index == \
+        custody_chunk_challenge.chunk_index
+
+    yield 'post', state
+
+
+def run_custody_chunk_response_processing(spec, state, custody_response, valid=True):
+    """
+    Run ``process_chunk_challenge_response``, yielding:
+      - pre-state ('pre')
+      - CustodyResponse ('custody_response')
+      - post-state ('post').
+    If ``valid == False``, run expecting ``AssertionError``
+    """
+    yield 'pre', state
+    yield 'custody_response', custody_response
+
+    if not valid:
+        expect_assertion_error(lambda: spec.process_custody_response(state, custody_response))
+        yield 'post', None
+        return
+
+    spec.process_chunk_challenge_response(state, custody_response)
+
+    assert state.custody_chunk_challenge_records[custody_response.challenge_index] == spec.CustodyChunkChallengeRecord()
+
+    yield 'post', state
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_challenge_appended(spec, state):
+    transition_to(spec, state, state.slot + 1)
+    shard = 0
+    offset_slots = spec.get_offset_slots(state, shard)
+    shard_transition = get_shard_transition(spec, state.slot, [2**15 // 3] * len(offset_slots))
+    data_index = 0
+    attestation = get_valid_on_time_attestation(spec, state, index=shard, signed=True, shard_transition_root=hash_tree_root(shard_transition))
+
+    transition_chunks = (shard_transition.shard_block_lengths[data_index] + spec.BYTES_PER_CUSTODY_CHUNK - 1) // spec.BYTES_PER_CUSTODY_CHUNK
+    test_vector = get_custody_test_vector(shard_transition.shard_block_lengths[data_index])
+    shard_root = get_custody_merkle_root(test_vector)
+
+    transition_to(spec, state, state.slot + spec.MIN_ATTESTATION_INCLUSION_DELAY)
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH * spec.EPOCHS_PER_CUSTODY_PERIOD)
+
+    challenge = get_valid_chunk_challenge(spec, state, attestation, shard_transition)
+
+    yield from run_chunk_challenge_processing(spec, state, challenge)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_multiple_epochs_custody(spec, state):
+    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH * 3)
+
+    shard = 0
+    offset_slots = spec.get_offset_slots(state, shard)
+    shard_transition = get_shard_transition(spec, state.slot, [2**15 // 3] * len(offset_slots))
+    data_index = 0
+    attestation = get_valid_on_time_attestation(spec, state, index=shard, signed=True, shard_transition_root=hash_tree_root(shard_transition))
+
+    transition_to(spec, state, state.slot + spec.MIN_ATTESTATION_INCLUSION_DELAY)
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH * (spec.EPOCHS_PER_CUSTODY_PERIOD - 1))
+
+    challenge = get_valid_chunk_challenge(spec, state, attestation, shard_transition)
+
+    yield from run_chunk_challenge_processing(spec, state, challenge)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_many_epochs_custody(spec, state):
+    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH * 100)
+
+    shard = 0
+    offset_slots = spec.get_offset_slots(state, shard)
+    shard_transition = get_shard_transition(spec, state.slot, [2**15 // 3] * len(offset_slots))
+    data_index = 0
+    attestation = get_valid_on_time_attestation(spec, state, index=shard, signed=True, shard_transition_root=hash_tree_root(shard_transition))
+
+    transition_to(spec, state, state.slot + spec.MIN_ATTESTATION_INCLUSION_DELAY)
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH * (spec.EPOCHS_PER_CUSTODY_PERIOD - 1))
+
+    challenge = get_valid_chunk_challenge(spec, state, attestation, shard_transition)
+
+    yield from run_chunk_challenge_processing(spec, state, challenge)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_off_chain_attestation(spec, state):
+    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH)
+
+    shard = 0
+    offset_slots = spec.get_offset_slots(state, shard)
+    shard_transition = get_shard_transition(spec, state.slot, [2**15 // 3] * len(offset_slots))
+    data_index = 0
+    attestation = get_valid_on_time_attestation(spec, state, index=shard, signed=True, shard_transition_root=hash_tree_root(shard_transition))
+
+    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH * (spec.EPOCHS_PER_CUSTODY_PERIOD - 1))
+
+    challenge = get_valid_chunk_challenge(spec, state, attestation, shard_transition)
+
+    yield from run_chunk_challenge_processing(spec, state, challenge)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_custody_response(spec, state):
+    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH)
+
+    shard = 0
+    offset_slots = spec.get_offset_slots(state, shard)
+    shard_transition = get_shard_transition(spec, state.slot, [2**15 // 3] * len(offset_slots))
+    data_index = 0
+    attestation = get_valid_on_time_attestation(spec, state, index=shard, signed=True, shard_transition_root=hash_tree_root(shard_transition))
+
+    transition_to(spec, state, state.slot + spec.MIN_ATTESTATION_INCLUSION_DELAY)
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH * (spec.EPOCHS_PER_CUSTODY_PERIOD - 1))
+
+    challenge = get_valid_chunk_challenge(spec, state, attestation, shard_transition)
+
+    _, _, _ = run_chunk_challenge_processing(spec, state, challenge)
+
+    chunk_challenge_index = state.custody_chunk_challenge_index - 1
+
+    custody_response = get_valid_custody_chunk_response(spec, state, challenge, 2**15 // 3, chunk_challenge_index)
+
+    yield from run_custody_chunk_response_processing(spec, state, custody_response)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_custody_response_multiple_epochs(spec, state):
+    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH * 3)
+
+    shard = 0
+    offset_slots = spec.get_offset_slots(state, shard)
+    shard_transition = get_shard_transition(spec, state.slot, [2**15 // 3] * len(offset_slots))
+    data_index = 0
+    attestation = get_valid_on_time_attestation(spec, state, index=shard, signed=True, shard_transition_root=hash_tree_root(shard_transition))
+
+    transition_to(spec, state, state.slot + spec.MIN_ATTESTATION_INCLUSION_DELAY)
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH * (spec.EPOCHS_PER_CUSTODY_PERIOD - 1))
+
+    challenge = get_valid_chunk_challenge(spec, state, attestation, shard_transition)
+
+    _, _, _ = run_chunk_challenge_processing(spec, state, challenge)
+
+    chunk_challenge_index = state.custody_chunk_challenge_index - 1
+
+    custody_response = get_valid_custody_chunk_response(spec, state, challenge, 2**15 // 3, chunk_challenge_index)
+
+    yield from run_custody_chunk_response_processing(spec, state, custody_response)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_custody_response_many_epochs(spec, state):
+    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH * 100)
+
+    shard = 0
+    offset_slots = spec.get_offset_slots(state, shard)
+    shard_transition = get_shard_transition(spec, state.slot, [2**15 // 3] * len(offset_slots))
+    data_index = 0
+    attestation = get_valid_on_time_attestation(spec, state, index=shard, signed=True, shard_transition_root=hash_tree_root(shard_transition))
+
+    transition_to(spec, state, state.slot + spec.MIN_ATTESTATION_INCLUSION_DELAY)
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    transition_to(spec, state, state.slot + spec.SLOTS_PER_EPOCH * (spec.EPOCHS_PER_CUSTODY_PERIOD - 1))
+
+    challenge = get_valid_chunk_challenge(spec, state, attestation, shard_transition)
+
+    _, _, _ = run_chunk_challenge_processing(spec, state, challenge)
+
+    chunk_challenge_index = state.custody_chunk_challenge_index - 1
+
+    custody_response = get_valid_custody_chunk_response(spec, state, challenge, 2**15 // 3, chunk_challenge_index)
+
+    yield from run_custody_chunk_response_processing(spec, state, custody_response)
diff --git a/tests/core/pyspec/eth2spec/test/phase_1/block_processing/test_process_custody_slashing.py b/tests/core/pyspec/eth2spec/test/phase_1/block_processing/test_process_custody_slashing.py
new file mode 100644
index 000000000..358aa5c0d
--- /dev/null
+++ b/tests/core/pyspec/eth2spec/test/phase_1/block_processing/test_process_custody_slashing.py
@@ -0,0 +1,349 @@
+from eth2spec.test.helpers.custody import (
+    get_valid_bit_challenge,
+    get_valid_custody_bit_response,
+    get_custody_test_vector,
+    get_custody_merkle_root,
+)
+from eth2spec.test.helpers.attestations import (
+    get_valid_attestation,
+)
+from eth2spec.utils.ssz.ssz_impl import hash_tree_root
+from eth2spec.test.helpers.state import next_epoch, get_balance
+from eth2spec.test.helpers.block import apply_empty_block
+from eth2spec.test.context import (
+    with_all_phases_except,
+    spec_state_test,
+    expect_assertion_error,
+)
+from eth2spec.test.phase_0.block_processing.test_process_attestation import run_attestation_processing
+
+
+def run_bit_challenge_processing(spec, state, custody_bit_challenge, valid=True):
+    """
+    Run ``process_bit_challenge``, yielding:
+      - pre-state ('pre')
+      - CustodyBitChallenge ('custody_bit_challenge')
+      - post-state ('post').
+    If ``valid == False``, run expecting ``AssertionError``
+    """
+    yield 'pre', state
+    yield 'custody_bit_challenge', custody_bit_challenge
+
+    if not valid:
+        expect_assertion_error(lambda: spec.process_bit_challenge(state, custody_bit_challenge))
+        yield 'post', None
+        return
+
+    spec.process_bit_challenge(state, custody_bit_challenge)
+
+    assert state.custody_bit_challenge_records[state.custody_bit_challenge_index - 1].chunk_bits_merkle_root == \
+        hash_tree_root(custody_bit_challenge.chunk_bits)
+    assert state.custody_bit_challenge_records[state.custody_bit_challenge_index - 1].challenger_index == \
+        custody_bit_challenge.challenger_index
+    assert state.custody_bit_challenge_records[state.custody_bit_challenge_index - 1].responder_index == \
+        custody_bit_challenge.responder_index
+
+    yield 'post', state
+
+
+def run_custody_bit_response_processing(spec, state, custody_response, valid=True):
+    """
+    Run ``process_bit_challenge_response``, yielding:
+      - pre-state ('pre')
+      - CustodyResponse ('custody_response')
+      - post-state ('post').
+    If ``valid == False``, run expecting ``AssertionError``
+    """
+    yield 'pre', state
+    yield 'custody_response', custody_response
+
+    if not valid:
+        expect_assertion_error(lambda: spec.process_custody_response(state, custody_response))
+        yield 'post', None
+        return
+
+    challenge = state.custody_bit_challenge_records[custody_response.challenge_index]
+    pre_slashed_balance = get_balance(state, challenge.challenger_index)
+
+    spec.process_custody_response(state, custody_response)
+
+    slashed_validator = state.validators[challenge.challenger_index]
+
+    assert slashed_validator.slashed
+    assert slashed_validator.exit_epoch < spec.FAR_FUTURE_EPOCH
+    assert slashed_validator.withdrawable_epoch < spec.FAR_FUTURE_EPOCH
+
+    assert get_balance(state, challenge.challenger_index) < pre_slashed_balance
+    yield 'post', state
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_challenge_appended(spec, state):
+    state.slot = spec.SLOTS_PER_EPOCH
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    attestation.custody_bits[0] = 0
+
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    state.slot += spec.SLOTS_PER_EPOCH * spec.EPOCHS_PER_CUSTODY_PERIOD
+
+    challenge = get_valid_bit_challenge(spec, state, attestation)
+
+    yield from run_bit_challenge_processing(spec, state, challenge)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_multiple_epochs_custody(spec, state):
+    state.slot = spec.SLOTS_PER_EPOCH * 3
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    attestation.custody_bits[0] = 0
+
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    state.slot += spec.SLOTS_PER_EPOCH * (spec.EPOCHS_PER_CUSTODY_PERIOD - 1)
+
+    challenge = get_valid_bit_challenge(spec, state, attestation)
+
+    yield from run_bit_challenge_processing(spec, state, challenge)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_many_epochs_custody(spec, state):
+    state.slot = spec.SLOTS_PER_EPOCH * 100
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    attestation.custody_bits[0] = 0
+
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    state.slot += spec.SLOTS_PER_EPOCH * (spec.EPOCHS_PER_CUSTODY_PERIOD - 1)
+
+    challenge = get_valid_bit_challenge(spec, state, attestation)
+
+    yield from run_bit_challenge_processing(spec, state, challenge)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_off_chain_attestation(spec, state):
+    state.slot = spec.SLOTS_PER_EPOCH
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    attestation.custody_bits[0] = 0
+
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+    state.slot += spec.SLOTS_PER_EPOCH * spec.EPOCHS_PER_CUSTODY_PERIOD
+
+    challenge = get_valid_bit_challenge(spec, state, attestation)
+
+    yield from run_bit_challenge_processing(spec, state, challenge)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_invalid_custody_bit_challenge(spec, state):
+    state.slot = spec.SLOTS_PER_EPOCH
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    attestation.custody_bits[0] = 0
+
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    state.slot += spec.SLOTS_PER_EPOCH * spec.EPOCHS_PER_CUSTODY_PERIOD
+
+    challenge = get_valid_bit_challenge(spec, state, attestation, invalid_custody_bit=True)
+
+    yield from run_bit_challenge_processing(spec, state, challenge, valid=False)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_max_reveal_lateness_1(spec, state):
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    attestation.custody_bits[0] = 0
+
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    challenge = get_valid_bit_challenge(spec, state, attestation)
+
+    responder_index = challenge.responder_index
+    target_epoch = attestation.data.target.epoch
+
+    state.validators[responder_index].max_reveal_lateness = 3
+
+    latest_reveal_epoch = spec.get_randao_epoch_for_custody_period(
+        spec.get_custody_period_for_validator(state, responder_index, target_epoch),
+        responder_index
+    ) + 2 * spec.EPOCHS_PER_CUSTODY_PERIOD + state.validators[responder_index].max_reveal_lateness
+
+    while spec.get_current_epoch(state) < latest_reveal_epoch - 2:
+        next_epoch(spec, state)
+        apply_empty_block(spec, state)
+
+    yield from run_bit_challenge_processing(spec, state, challenge)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_max_reveal_lateness_2(spec, state):
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    attestation.custody_bits[0] = 0
+
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    challenge = get_valid_bit_challenge(spec, state, attestation)
+
+    responder_index = challenge.responder_index
+
+    state.validators[responder_index].max_reveal_lateness = 3
+
+    for i in range(spec.get_randao_epoch_for_custody_period(
+        spec.get_custody_period_for_validator(state, responder_index),
+        responder_index
+    ) + 2 * spec.EPOCHS_PER_CUSTODY_PERIOD + state.validators[responder_index].max_reveal_lateness - 1):
+        next_epoch(spec, state)
+        apply_empty_block(spec, state)
+
+    yield from run_bit_challenge_processing(spec, state, challenge, False)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_custody_response(spec, state):
+    state.slot = spec.SLOTS_PER_EPOCH
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    attestation.custody_bits[0] = 0
+
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    state.slot += spec.SLOTS_PER_EPOCH * spec.EPOCHS_PER_CUSTODY_PERIOD
+
+    challenge = get_valid_bit_challenge(spec, state, attestation)
+
+    _, _, _ = run_bit_challenge_processing(spec, state, challenge)
+
+    bit_challenge_index = state.custody_bit_challenge_index - 1
+
+    custody_response = get_valid_custody_bit_response(spec, state, challenge, test_vector, bit_challenge_index)
+
+    yield from run_custody_bit_response_processing(spec, state, custody_response)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_custody_response_multiple_epochs(spec, state):
+    state.slot = spec.SLOTS_PER_EPOCH * 3
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    attestation.custody_bits[0] = 0
+
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    state.slot += spec.SLOTS_PER_EPOCH * spec.EPOCHS_PER_CUSTODY_PERIOD
+
+    challenge = get_valid_bit_challenge(spec, state, attestation)
+
+    _, _, _ = run_bit_challenge_processing(spec, state, challenge)
+
+    bit_challenge_index = state.custody_bit_challenge_index - 1
+
+    custody_response = get_valid_custody_bit_response(spec, state, challenge, test_vector, bit_challenge_index)
+
+    yield from run_custody_bit_response_processing(spec, state, custody_response)
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_custody_response_many_epochs(spec, state):
+    state.slot = spec.SLOTS_PER_EPOCH * 100
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    attestation.custody_bits[0] = 0
+
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    state.slot += spec.SLOTS_PER_EPOCH * spec.EPOCHS_PER_CUSTODY_PERIOD
+
+    challenge = get_valid_bit_challenge(spec, state, attestation)
+
+    _, _, _ = run_bit_challenge_processing(spec, state, challenge)
+
+    bit_challenge_index = state.custody_bit_challenge_index - 1
+
+    custody_response = get_valid_custody_bit_response(spec, state, challenge, test_vector, bit_challenge_index)
+
+    yield from run_custody_bit_response_processing(spec, state, custody_response)
diff --git a/tests/core/pyspec/eth2spec/test/phase_1/epoch_processing/test_process_final_custody_updates.py b/tests/core/pyspec/eth2spec/test/phase_1/epoch_processing/test_process_final_custody_updates.py
new file mode 100644
index 000000000..d200ed2b3
--- /dev/null
+++ b/tests/core/pyspec/eth2spec/test/phase_1/epoch_processing/test_process_final_custody_updates.py
@@ -0,0 +1,319 @@
+from eth2spec.test.helpers.custody import (
+    get_valid_bit_challenge,
+    get_valid_chunk_challenge,
+    get_valid_custody_bit_response,
+    get_valid_custody_chunk_response,
+    get_valid_custody_key_reveal,
+    get_custody_test_vector,
+    get_custody_merkle_root,
+)
+from eth2spec.test.helpers.attestations import (
+    get_valid_attestation,
+)
+from eth2spec.test.helpers.state import next_epoch
+from eth2spec.test.helpers.block import apply_empty_block
+from eth2spec.test.context import (
+    with_all_phases_except,
+    spec_state_test,
+)
+from eth2spec.test.phase_0.block_processing.test_process_attestation import run_attestation_processing
+from eth2spec.test.phase_0.epoch_processing.run_epoch_process_base import run_epoch_processing_with
+
+from eth2spec.test.phase_1.block_processing.test_process_bit_challenge import (
+    run_bit_challenge_processing,
+    run_custody_bit_response_processing,
+)
+from eth2spec.test.phase_1.block_processing.test_process_chunk_challenge import (
+    run_chunk_challenge_processing,
+    run_custody_chunk_response_processing,
+)
+from eth2spec.test.phase_1.block_processing.test_process_custody_key_reveal import run_custody_key_reveal_processing
+
+
+def run_process_final_custody_updates(spec, state):
+    yield from run_epoch_processing_with(spec, state, 'process_final_custody_updates')
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_validator_withdrawal_delay(spec, state):
+    spec.initiate_validator_exit(state, 0)
+    assert state.validators[0].withdrawable_epoch < spec.FAR_FUTURE_EPOCH
+
+    yield from run_process_final_custody_updates(spec, state)
+
+    assert state.validators[0].withdrawable_epoch == spec.FAR_FUTURE_EPOCH
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_validator_withdrawal_reenable_after_custody_reveal(spec, state):
+    spec.initiate_validator_exit(state, 0)
+    assert state.validators[0].withdrawable_epoch < spec.FAR_FUTURE_EPOCH
+
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    assert state.validators[0].withdrawable_epoch == spec.FAR_FUTURE_EPOCH
+
+    while spec.get_current_epoch(state) < state.validators[0].exit_epoch:
+        next_epoch(spec, state)
+        apply_empty_block(spec, state)
+
+    while (state.validators[0].next_custody_secret_to_reveal
+           <= spec.get_custody_period_for_validator(state, 0, state.validators[0].exit_epoch - 1)):
+        custody_key_reveal = get_valid_custody_key_reveal(spec, state, validator_index=0)
+        _, _, _ = run_custody_key_reveal_processing(spec, state, custody_key_reveal)
+
+    yield from run_process_final_custody_updates(spec, state)
+
+    assert state.validators[0].withdrawable_epoch < spec.FAR_FUTURE_EPOCH
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_validator_withdrawal_suspend_after_bit_challenge(spec, state):
+    state.slot = spec.SLOTS_PER_EPOCH
+
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    attestation.custody_bits[0] = 0
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    validator_index = spec.get_crosslink_committee(
+        state,
+        attestation.data.target.epoch,
+        attestation.data.crosslink.shard
+    )[0]
+
+    spec.initiate_validator_exit(state, validator_index)
+    assert state.validators[validator_index].withdrawable_epoch < spec.FAR_FUTURE_EPOCH
+
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    assert state.validators[validator_index].withdrawable_epoch == spec.FAR_FUTURE_EPOCH
+
+    while spec.get_current_epoch(state) < state.validators[validator_index].exit_epoch:
+        next_epoch(spec, state)
+        apply_empty_block(spec, state)
+
+    while (state.validators[validator_index].next_custody_secret_to_reveal
+           <= spec.get_custody_period_for_validator(
+               state,
+               validator_index,
+               state.validators[validator_index].exit_epoch - 1)):
+        custody_key_reveal = get_valid_custody_key_reveal(spec, state, validator_index=validator_index)
+        _, _, _ = run_custody_key_reveal_processing(spec, state, custody_key_reveal)
+
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    challenge = get_valid_bit_challenge(spec, state, attestation)
+
+    _, _, _ = run_bit_challenge_processing(spec, state, challenge)
+
+    yield from run_process_final_custody_updates(spec, state)
+
+    assert state.validators[validator_index].withdrawable_epoch == spec.FAR_FUTURE_EPOCH
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_validator_withdrawal_suspend_after_chunk_challenge(spec, state):
+    state.slot = spec.SLOTS_PER_EPOCH
+
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    attestation.custody_bits[0] = 0
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    validator_index = spec.get_crosslink_committee(
+        state,
+        attestation.data.target.epoch,
+        attestation.data.crosslink.shard
+    )[0]
+
+    spec.initiate_validator_exit(state, validator_index)
+    assert state.validators[validator_index].withdrawable_epoch < spec.FAR_FUTURE_EPOCH
+
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    assert state.validators[validator_index].withdrawable_epoch == spec.FAR_FUTURE_EPOCH
+
+    while spec.get_current_epoch(state) < state.validators[validator_index].exit_epoch:
+        next_epoch(spec, state)
+        apply_empty_block(spec, state)
+
+    while (state.validators[validator_index].next_custody_secret_to_reveal
+           <= spec.get_custody_period_for_validator(
+               state,
+               validator_index,
+               state.validators[validator_index].exit_epoch - 1)):
+        custody_key_reveal = get_valid_custody_key_reveal(spec, state, validator_index=validator_index)
+        _, _, _ = run_custody_key_reveal_processing(spec, state, custody_key_reveal)
+
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    challenge = get_valid_chunk_challenge(spec, state, attestation)
+
+    _, _, _ = run_chunk_challenge_processing(spec, state, challenge)
+
+    yield from run_process_final_custody_updates(spec, state)
+
+    assert state.validators[validator_index].withdrawable_epoch == spec.FAR_FUTURE_EPOCH
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_validator_withdrawal_resume_after_bit_challenge_response(spec, state):
+    state.slot = spec.SLOTS_PER_EPOCH
+
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    attestation.custody_bits[0] = 0
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    validator_index = spec.get_crosslink_committee(
+        state,
+        attestation.data.target.epoch,
+        attestation.data.crosslink.shard
+    )[0]
+
+    spec.initiate_validator_exit(state, validator_index)
+    assert state.validators[validator_index].withdrawable_epoch < spec.FAR_FUTURE_EPOCH
+
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    assert state.validators[validator_index].withdrawable_epoch == spec.FAR_FUTURE_EPOCH
+
+    while spec.get_current_epoch(state) < state.validators[validator_index].exit_epoch:
+        next_epoch(spec, state)
+        apply_empty_block(spec, state)
+
+    while (state.validators[validator_index].next_custody_secret_to_reveal
+           <= spec.get_custody_period_for_validator(
+               state,
+               validator_index,
+               state.validators[validator_index].exit_epoch - 1)):
+        custody_key_reveal = get_valid_custody_key_reveal(spec, state, validator_index=validator_index)
+        _, _, _ = run_custody_key_reveal_processing(spec, state, custody_key_reveal)
+
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    challenge = get_valid_bit_challenge(spec, state, attestation)
+
+    _, _, _ = run_bit_challenge_processing(spec, state, challenge)
+
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    assert state.validators[validator_index].withdrawable_epoch == spec.FAR_FUTURE_EPOCH
+
+    bit_challenge_index = state.custody_bit_challenge_index - 1
+    response = get_valid_custody_bit_response(
+        spec,
+        state,
+        challenge,
+        test_vector,
+        bit_challenge_index,
+        invalid_chunk_bit=False)
+
+    _, _, _ = run_custody_bit_response_processing(spec, state, response)
+
+    yield from run_process_final_custody_updates(spec, state)
+
+    assert state.validators[validator_index].withdrawable_epoch < spec.FAR_FUTURE_EPOCH
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_validator_withdrawal_resume_after_chunk_challenge_response(spec, state):
+    state.slot = spec.SLOTS_PER_EPOCH
+
+    attestation = get_valid_attestation(spec, state, signed=True)
+
+    test_vector = get_custody_test_vector(
+        spec.get_custody_chunk_count(attestation.data.crosslink) * spec.BYTES_PER_CUSTODY_CHUNK)
+    shard_root = get_custody_merkle_root(test_vector)
+    attestation.data.crosslink.data_root = shard_root
+    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    _, _, _ = run_attestation_processing(spec, state, attestation)
+
+    validator_index = spec.get_crosslink_committee(
+        state,
+        attestation.data.target.epoch,
+        attestation.data.crosslink.shard
+    )[0]
+
+    spec.initiate_validator_exit(state, validator_index)
+    assert state.validators[validator_index].withdrawable_epoch < spec.FAR_FUTURE_EPOCH
+
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    assert state.validators[validator_index].withdrawable_epoch == spec.FAR_FUTURE_EPOCH
+
+    while spec.get_current_epoch(state) < state.validators[validator_index].exit_epoch:
+        next_epoch(spec, state)
+        apply_empty_block(spec, state)
+
+    while (state.validators[validator_index].next_custody_secret_to_reveal
+           <= spec.get_custody_period_for_validator(
+               state,
+               validator_index,
+               state.validators[validator_index].exit_epoch - 1)):
+        custody_key_reveal = get_valid_custody_key_reveal(spec, state, validator_index=validator_index)
+        _, _, _ = run_custody_key_reveal_processing(spec, state, custody_key_reveal)
+
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    challenge = get_valid_chunk_challenge(spec, state, attestation)
+
+    _, _, _ = run_chunk_challenge_processing(spec, state, challenge)
+
+    next_epoch(spec, state)
+    apply_empty_block(spec, state)
+
+    assert state.validators[validator_index].withdrawable_epoch == spec.FAR_FUTURE_EPOCH
+
+    chunk_challenge_index = state.custody_chunk_challenge_index - 1
+    response = get_valid_custody_chunk_response(spec, state, challenge, test_vector, chunk_challenge_index)
+
+    _, _, _ = run_custody_chunk_response_processing(spec, state, response)
+
+    yield from run_process_final_custody_updates(spec, state)
+
+    assert state.validators[validator_index].withdrawable_epoch < spec.FAR_FUTURE_EPOCH
diff --git a/tests/core/pyspec/eth2spec/test/phase_1/epoch_processing/test_process_reveal_deadlines.py b/tests/core/pyspec/eth2spec/test/phase_1/epoch_processing/test_process_reveal_deadlines.py
new file mode 100644
index 000000000..688b046c8
--- /dev/null
+++ b/tests/core/pyspec/eth2spec/test/phase_1/epoch_processing/test_process_reveal_deadlines.py
@@ -0,0 +1,46 @@
+from eth2spec.test.helpers.custody import (
+    get_valid_custody_key_reveal,
+)
+from eth2spec.test.helpers.state import next_epoch
+from eth2spec.test.context import (
+    with_all_phases_except,
+    spec_state_test,
+)
+from eth2spec.test.phase_0.epoch_processing.run_epoch_process_base import run_epoch_processing_with
+from eth2spec.test.phase_1.block_processing.test_process_custody_key_reveal import run_custody_key_reveal_processing
+
+
+def run_process_challenge_deadlines(spec, state):
+    yield from run_epoch_processing_with(spec, state, 'process_challenge_deadlines')
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_validator_slashed_after_reveal_deadline(spec, state):
+    assert state.validators[0].slashed == 0
+
+    state.slot += ((spec.CHUNK_RESPONSE_DEADLINE + spec.EPOCHS_PER_CUSTODY_PERIOD)
+                   * spec.SLOTS_PER_EPOCH)
+    next_epoch(spec, state)
+
+    yield from run_process_challenge_deadlines(spec, state)
+
+    assert state.validators[0].slashed == 1
+
+
+@with_all_phases_except(['phase0'])
+@spec_state_test
+def test_validator_not_slashed_after_reveal(spec, state):
+    state.slot += spec.EPOCHS_PER_CUSTODY_PERIOD * spec.SLOTS_PER_EPOCH
+    custody_key_reveal = get_valid_custody_key_reveal(spec, state)
+
+    _, _, _ = run_custody_key_reveal_processing(spec, state, custody_key_reveal)
+
+    assert state.validators[0].slashed == 0
+
+    state.slot += spec.CHUNK_RESPONSE_DEADLINE * spec.SLOTS_PER_EPOCH
+    next_epoch(spec, state)
+
+    yield from run_process_challenge_deadlines(spec, state)
+
+    assert state.validators[0].slashed == 0