diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index 838d9d681..b57aa7ff4 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -84,7 +84,6 @@
             - [`get_committee_count`](#get_committee_count)
             - [`get_crosslink_committee`](#get_crosslink_committee)
             - [`get_beacon_proposer_index`](#get_beacon_proposer_index)
-            - [`get_attestation_data_slot`](#get_attestation_data_slot)
             - [`get_total_balance`](#get_total_balance)
             - [`get_total_active_balance`](#get_total_active_balance)
             - [`get_domain`](#get_domain)
diff --git a/specs/core/1_shard-data-chains.md b/specs/core/1_shard-data-chains.md
index 69962b6fe..9bd9c70ee 100644
--- a/specs/core/1_shard-data-chains.md
+++ b/specs/core/1_shard-data-chains.md
@@ -53,6 +53,7 @@ This document describes the shard transition function (data layer only) and the
 
 | Name | SSZ equivalent | Description |
 | - | - | - |
+| `Shard` | `uint64` | a shard number |
 | `ShardSlot` | `uint64` | a shard slot number |
 
 ## Configuration
@@ -101,6 +102,14 @@ This document describes the shard transition function (data layer only) and the
 
 ## Containers
 
+### `Crosslink`
+
+```python
+class Crosslink(Container):
+    # STUB: placeholder data structure while reworking phase 0
+    shard: Shard
+```
+ 
 ### `ShardBlock`
 
 ```python
diff --git a/test_libs/pyspec/eth2spec/test/helpers/attestations.py b/test_libs/pyspec/eth2spec/test/helpers/attestations.py
index 23d1a8f8f..00c25b340 100644
--- a/test_libs/pyspec/eth2spec/test/helpers/attestations.py
+++ b/test_libs/pyspec/eth2spec/test/helpers/attestations.py
@@ -3,11 +3,10 @@ from typing import List
 from eth2spec.test.helpers.block import build_empty_block_for_next_slot, sign_block
 from eth2spec.test.helpers.keys import privkeys
 from eth2spec.utils.bls import bls_sign, bls_aggregate_signatures
-from eth2spec.utils.ssz.ssz_impl import hash_tree_root
 from eth2spec.utils.ssz.ssz_typing import Bitlist
 
 
-def build_attestation_data(spec, state, slot, shard):
+def build_attestation_data(spec, state, slot, index):
     assert state.slot >= slot
 
     if slot == state.slot:
@@ -30,40 +29,27 @@ def build_attestation_data(spec, state, slot, shard):
         source_epoch = state.current_justified_checkpoint.epoch
         source_root = state.current_justified_checkpoint.root
 
-    if spec.compute_epoch_of_slot(slot) == spec.get_current_epoch(state):
-        parent_crosslink = state.current_crosslinks[shard]
-    else:
-        parent_crosslink = state.previous_crosslinks[shard]
-
     return spec.AttestationData(
+        slot=slot,
         beacon_block_root=block_root,
         source=spec.Checkpoint(epoch=source_epoch, root=source_root),
         target=spec.Checkpoint(epoch=spec.compute_epoch_of_slot(slot), root=epoch_boundary_root),
-        crosslink=spec.Crosslink(
-            shard=shard,
-            start_epoch=parent_crosslink.end_epoch,
-            end_epoch=min(spec.compute_epoch_of_slot(slot), parent_crosslink.end_epoch + spec.MAX_EPOCHS_PER_CROSSLINK),
-            data_root=spec.Hash(),
-            parent_root=hash_tree_root(parent_crosslink),
-        ),
+        index=index,
     )
 
 
-def get_valid_attestation(spec, state, slot=None, signed=False):
+def get_valid_attestation(spec, state, slot=None, index=None, signed=False):
     if slot is None:
         slot = state.slot
+    if index is None:
+        index = 0
 
-    epoch = spec.compute_epoch_of_slot(slot)
-    epoch_start_shard = spec.get_start_shard(state, epoch)
-    committees_per_slot = spec.get_committee_count(state, epoch) // spec.SLOTS_PER_EPOCH
-    shard = (epoch_start_shard + committees_per_slot * (slot % spec.SLOTS_PER_EPOCH)) % spec.SHARD_COUNT
-
-    attestation_data = build_attestation_data(spec, state, slot, shard)
+    attestation_data = build_attestation_data(spec, state, slot, index)
 
     crosslink_committee = spec.get_crosslink_committee(
         state,
         attestation_data.target.epoch,
-        attestation_data.crosslink.shard,
+        attestation_data.index,
     )
 
     committee_size = len(crosslink_committee)
@@ -132,7 +118,7 @@ def fill_aggregate_attestation(spec, state, attestation):
     crosslink_committee = spec.get_crosslink_committee(
         state,
         attestation.data.target.epoch,
-        attestation.data.crosslink.shard,
+        attestation.data.index,
     )
     for i in range(len(crosslink_committee)):
         attestation.aggregation_bits[i] = True
diff --git a/test_libs/pyspec/eth2spec/test/phase_0/block_processing/test_process_attestation.py b/test_libs/pyspec/eth2spec/test/phase_0/block_processing/test_process_attestation.py
index 8ae45788f..b3952b7ea 100644
--- a/test_libs/pyspec/eth2spec/test/phase_0/block_processing/test_process_attestation.py
+++ b/test_libs/pyspec/eth2spec/test/phase_0/block_processing/test_process_attestation.py
@@ -1,4 +1,9 @@
-from eth2spec.test.context import spec_state_test, expect_assertion_error, always_bls, with_all_phases, with_phases
+from eth2spec.test.context import (
+    spec_state_test,
+    expect_assertion_error,
+    always_bls, never_bls,
+    with_all_phases, with_phases,
+)
 from eth2spec.test.helpers.attestations import (
     get_valid_attestation,
     sign_aggregate_attestation,
@@ -6,7 +11,6 @@ from eth2spec.test.helpers.attestations import (
 )
 from eth2spec.test.helpers.state import (
     next_epoch,
-    next_slot,
 )
 from eth2spec.test.helpers.block import apply_empty_block
 from eth2spec.utils.ssz.ssz_typing import Bitlist
@@ -67,54 +71,6 @@ def test_success_previous_epoch(spec, state):
     yield from run_attestation_processing(spec, state, attestation)
 
 
-@with_all_phases
-@spec_state_test
-def test_success_since_max_epochs_per_crosslink(spec, state):
-    # Do not run mainnet (64 epochs), that would mean the equivalent of ~7 hours chain simulation.
-    if spec.MAX_EPOCHS_PER_CROSSLINK > 4:
-        return
-    for _ in range(spec.MAX_EPOCHS_PER_CROSSLINK + 2):
-        next_epoch(spec, state)
-    apply_empty_block(spec, state)
-
-    attestation = get_valid_attestation(spec, state, signed=True)
-    data = attestation.data
-    # test logic sanity check: make sure the attestation only includes MAX_EPOCHS_PER_CROSSLINK epochs
-    assert data.crosslink.end_epoch - data.crosslink.start_epoch == spec.MAX_EPOCHS_PER_CROSSLINK
-
-    for _ in range(spec.MIN_ATTESTATION_INCLUSION_DELAY):
-        next_slot(spec, state)
-    apply_empty_block(spec, state)
-
-    yield from run_attestation_processing(spec, state, attestation)
-
-
-@with_all_phases
-@spec_state_test
-def test_wrong_end_epoch_with_max_epochs_per_crosslink(spec, state):
-    # Do not run mainnet (64 epochs), that would mean the equivalent of ~7 hours chain simulation.
-    if spec.MAX_EPOCHS_PER_CROSSLINK > 4:
-        return
-    for _ in range(spec.MAX_EPOCHS_PER_CROSSLINK + 2):
-        next_epoch(spec, state)
-    apply_empty_block(spec, state)
-
-    attestation = get_valid_attestation(spec, state)
-    data = attestation.data
-    # test logic sanity check: make sure the attestation only includes MAX_EPOCHS_PER_CROSSLINK epochs
-    assert data.crosslink.end_epoch - data.crosslink.start_epoch == spec.MAX_EPOCHS_PER_CROSSLINK
-    # Now change it to be different
-    data.crosslink.end_epoch += 1
-
-    sign_attestation(spec, state, attestation)
-
-    for _ in range(spec.MIN_ATTESTATION_INCLUSION_DELAY):
-        next_slot(spec, state)
-    apply_empty_block(spec, state)
-
-    yield from run_attestation_processing(spec, state, attestation, False)
-
-
 @with_all_phases
 @spec_state_test
 @always_bls
@@ -168,27 +124,13 @@ def test_old_source_epoch(spec, state):
 
 @with_all_phases
 @spec_state_test
-def test_wrong_shard(spec, state):
-    attestation = get_valid_attestation(spec, state)
-    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
-
-    attestation.data.crosslink.shard += 1
-
-    sign_attestation(spec, state, attestation)
-
-    yield from run_attestation_processing(spec, state, attestation, False)
-
-
-@with_all_phases
-@spec_state_test
-def test_invalid_shard(spec, state):
+@never_bls
+def test_invalid_index(spec, state):
     attestation = get_valid_attestation(spec, state)
     state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
 
     # off by one (with respect to valid range) on purpose
-    attestation.data.crosslink.shard = spec.SHARD_COUNT
-
-    sign_attestation(spec, state, attestation)
+    attestation.data.index = spec.COMMITTEES_PER_SLOT
 
     yield from run_attestation_processing(spec, state, attestation, False)
 
@@ -290,73 +232,6 @@ def test_bad_source_root(spec, state):
     yield from run_attestation_processing(spec, state, attestation, False)
 
 
-@with_phases(['phase0'])
-@spec_state_test
-def test_non_zero_crosslink_data_root(spec, state):
-    attestation = get_valid_attestation(spec, state)
-    state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY
-
-    attestation.data.crosslink.data_root = b'\x42' * 32
-
-    sign_attestation(spec, state, attestation)
-
-    yield from run_attestation_processing(spec, state, attestation, False)
-
-
-@with_all_phases
-@spec_state_test
-def test_bad_parent_crosslink(spec, state):
-    state.slot = spec.SLOTS_PER_EPOCH - 1
-    next_epoch(spec, state)
-    apply_empty_block(spec, state)
-
-    attestation = get_valid_attestation(spec, state, signed=False)
-    for _ in range(spec.MIN_ATTESTATION_INCLUSION_DELAY):
-        next_slot(spec, state)
-    apply_empty_block(spec, state)
-
-    attestation.data.crosslink.parent_root = b'\x27' * 32
-    sign_attestation(spec, state, attestation)
-
-    yield from run_attestation_processing(spec, state, attestation, False)
-
-
-@with_all_phases
-@spec_state_test
-def test_bad_crosslink_start_epoch(spec, state):
-    state.slot = spec.SLOTS_PER_EPOCH - 1
-    next_epoch(spec, state)
-    apply_empty_block(spec, state)
-
-    attestation = get_valid_attestation(spec, state, signed=False)
-    for _ in range(spec.MIN_ATTESTATION_INCLUSION_DELAY):
-        next_slot(spec, state)
-    apply_empty_block(spec, state)
-
-    attestation.data.crosslink.start_epoch += 1
-    sign_attestation(spec, state, attestation)
-
-    yield from run_attestation_processing(spec, state, attestation, False)
-
-
-@with_all_phases
-@spec_state_test
-def test_bad_crosslink_end_epoch(spec, state):
-    state.slot = spec.SLOTS_PER_EPOCH - 1
-    next_epoch(spec, state)
-    apply_empty_block(spec, state)
-
-    attestation = get_valid_attestation(spec, state, signed=False)
-    for _ in range(spec.MIN_ATTESTATION_INCLUSION_DELAY):
-        next_slot(spec, state)
-    apply_empty_block(spec, state)
-
-    attestation.data.crosslink.end_epoch += 1
-    sign_attestation(spec, state, attestation)
-
-    yield from run_attestation_processing(spec, state, attestation, False)
-
-
 @with_all_phases
 @spec_state_test
 def test_inconsistent_bits(spec, state):
diff --git a/test_libs/pyspec/eth2spec/test/phase_0/epoch_processing/test_process_crosslinks.py b/test_libs/pyspec/eth2spec/test/phase_0/epoch_processing/test_process_crosslinks.py
deleted file mode 100644
index 41d784c50..000000000
--- a/test_libs/pyspec/eth2spec/test/phase_0/epoch_processing/test_process_crosslinks.py
+++ /dev/null
@@ -1,132 +0,0 @@
-from copy import deepcopy
-
-from eth2spec.test.context import spec_state_test, with_all_phases
-from eth2spec.test.helpers.state import (
-    next_epoch,
-    next_slot
-)
-from eth2spec.test.helpers.block import apply_empty_block
-from eth2spec.test.helpers.attestations import (
-    add_attestation_to_state,
-    fill_aggregate_attestation,
-    get_valid_attestation,
-    sign_attestation,
-)
-from eth2spec.test.phase_0.epoch_processing.run_epoch_process_base import run_epoch_processing_with
-
-
-def run_process_crosslinks(spec, state):
-    yield from run_epoch_processing_with(spec, state, 'process_crosslinks')
-
-
-@with_all_phases
-@spec_state_test
-def test_no_attestations(spec, state):
-    yield from run_process_crosslinks(spec, state)
-
-    for shard in range(spec.SHARD_COUNT):
-        assert state.previous_crosslinks[shard] == state.current_crosslinks[shard]
-
-
-@with_all_phases
-@spec_state_test
-def test_single_crosslink_update_from_current_epoch(spec, state):
-    next_epoch(spec, state)
-
-    attestation = get_valid_attestation(spec, state, signed=True)
-
-    fill_aggregate_attestation(spec, state, attestation)
-    add_attestation_to_state(spec, state, attestation, state.slot + spec.MIN_ATTESTATION_INCLUSION_DELAY)
-
-    assert len(state.current_epoch_attestations) == 1
-
-    shard = attestation.data.crosslink.shard
-    pre_crosslink = deepcopy(state.current_crosslinks[shard])
-
-    yield from run_process_crosslinks(spec, state)
-
-    assert state.previous_crosslinks[shard] != state.current_crosslinks[shard]
-    assert pre_crosslink != state.current_crosslinks[shard]
-
-
-@with_all_phases
-@spec_state_test
-def test_single_crosslink_update_from_previous_epoch(spec, state):
-    next_epoch(spec, state)
-
-    attestation = get_valid_attestation(spec, state, signed=True)
-
-    fill_aggregate_attestation(spec, state, attestation)
-    add_attestation_to_state(spec, state, attestation, state.slot + spec.SLOTS_PER_EPOCH)
-
-    assert len(state.previous_epoch_attestations) == 1
-
-    shard = attestation.data.crosslink.shard
-    pre_crosslink = deepcopy(state.current_crosslinks[shard])
-
-    crosslink_deltas = spec.get_crosslink_deltas(state)
-
-    yield from run_process_crosslinks(spec, state)
-
-    assert state.previous_crosslinks[shard] != state.current_crosslinks[shard]
-    assert pre_crosslink != state.current_crosslinks[shard]
-
-    # ensure rewarded
-    for index in spec.get_crosslink_committee(
-            state,
-            attestation.data.target.epoch,
-            attestation.data.crosslink.shard):
-        assert crosslink_deltas[0][index] > 0
-        assert crosslink_deltas[1][index] == 0
-
-
-@with_all_phases
-@spec_state_test
-def test_double_late_crosslink(spec, state):
-    if spec.get_committee_count(state, spec.get_current_epoch(state)) < spec.SHARD_COUNT:
-        print("warning: ignoring test, test-assumptions are incompatible with configuration")
-        return
-
-    next_epoch(spec, state)
-    state.slot += 4
-
-    attestation_1 = get_valid_attestation(spec, state, signed=True)
-    fill_aggregate_attestation(spec, state, attestation_1)
-
-    # add attestation_1 to next epoch
-    next_epoch(spec, state)
-    add_attestation_to_state(spec, state, attestation_1, state.slot + 1)
-
-    for _ in range(spec.SLOTS_PER_EPOCH):
-        attestation_2 = get_valid_attestation(spec, state)
-        if attestation_2.data.crosslink.shard == attestation_1.data.crosslink.shard:
-            sign_attestation(spec, state, attestation_2)
-            break
-        next_slot(spec, state)
-    apply_empty_block(spec, state)
-
-    fill_aggregate_attestation(spec, state, attestation_2)
-
-    # add attestation_2 in the next epoch after attestation_1 has
-    # already updated the relevant crosslink
-    next_epoch(spec, state)
-    add_attestation_to_state(spec, state, attestation_2, state.slot + 1)
-
-    assert len(state.previous_epoch_attestations) == 1
-    assert len(state.current_epoch_attestations) == 0
-
-    crosslink_deltas = spec.get_crosslink_deltas(state)
-
-    yield from run_process_crosslinks(spec, state)
-
-    shard = attestation_2.data.crosslink.shard
-
-    # ensure that the current crosslinks were not updated by the second attestation
-    assert state.previous_crosslinks[shard] == state.current_crosslinks[shard]
-    # ensure no reward, only penalties for the failed crosslink
-    for index in spec.get_crosslink_committee(
-            state,
-            attestation_2.data.target.epoch,
-            attestation_2.data.crosslink.shard):
-        assert crosslink_deltas[0][index] == 0
-        assert crosslink_deltas[1][index] > 0