diff --git a/tensorflow_privacy/privacy/sparsity_preserving_noise/BUILD b/tensorflow_privacy/privacy/sparsity_preserving_noise/BUILD
new file mode 100644
index 0000000..e28361d
--- /dev/null
+++ b/tensorflow_privacy/privacy/sparsity_preserving_noise/BUILD
@@ -0,0 +1,14 @@
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])
+
+py_library(
+    name = "type_aliases",
+    srcs = ["type_aliases.py"],
+)
+
+py_library(
+    name = "layer_registry",
+    srcs = ["layer_registry.py"],
+    deps = [":type_aliases"],
+)
diff --git a/tensorflow_privacy/privacy/sparsity_preserving_noise/layer_registry.py b/tensorflow_privacy/privacy/sparsity_preserving_noise/layer_registry.py
new file mode 100644
index 0000000..6c7d9a4
--- /dev/null
+++ b/tensorflow_privacy/privacy/sparsity_preserving_noise/layer_registry.py
@@ -0,0 +1,51 @@
+# Copyright 2024, The TensorFlow Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Registry of layer classes to their contribution histogram functions."""
+
+from typing import Type
+
+import tensorflow as tf
+from tensorflow_privacy.privacy.sparsity_preserving_noise import type_aliases
+
+
+# ==============================================================================
+# Main class
+# ==============================================================================
+class LayerRegistry:
+  """Custom container for layer registry functions."""
+
+  def __init__(self):
+    """Basic initialization of various internal dictionaries."""
+    self._layer_class_dict = {}
+    self._registry = {}
+
+  def is_elem(self, layer_instance: tf.keras.layers.Layer) -> bool:
+    """Checks if a layer instance's class is in the registry."""
+    return hash(layer_instance.__class__) in self._registry
+
+  def lookup(
+      self, layer_instance: tf.keras.layers.Layer
+  ) -> type_aliases.SparsityPreservingNoiseLayerRegistryFunction:
+    """Returns the layer registry function for a given layer instance."""
+    return self._registry[hash(layer_instance.__class__)]
+
+  def insert(
+      self,
+      layer_class: Type[tf.keras.layers.Layer],
+      layer_registry_function: type_aliases.SparsityPreservingNoiseLayerRegistryFunction,
+  ):
+    """Inserts a layer registry function into the internal dictionaries."""
+    layer_key = hash(layer_class)
+    self._layer_class_dict[layer_key] = layer_class
+    self._registry[layer_key] = layer_registry_function
diff --git a/tensorflow_privacy/privacy/sparsity_preserving_noise/type_aliases.py b/tensorflow_privacy/privacy/sparsity_preserving_noise/type_aliases.py
new file mode 100644
index 0000000..c63d083
--- /dev/null
+++ b/tensorflow_privacy/privacy/sparsity_preserving_noise/type_aliases.py
@@ -0,0 +1,31 @@
+# Copyright 2024, The TensorFlow Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Type aliases for sparsity preserving noise."""
+
+from collections.abc import Callable, Mapping, Sequence
+from typing import Any
+import tensorflow as tf
+
+InputArgs = Sequence[Any]
+InputKwargs = Mapping[str, Any]
+SparseGradient = tf.IndexedSlices
+ContributionCountHistogram = tf.SparseTensor
+ContributionCountHistogramFn = Callable[
+    [SparseGradient], Mapping[str, ContributionCountHistogram]
+]
+NumMicrobatches = int | tf.Tensor
+SparsityPreservingNoiseLayerRegistryFunction = Callable[
+    [tf.keras.layers.Layer, InputArgs, InputKwargs, NumMicrobatches | None],
+    ContributionCountHistogramFn,
+]