diff --git a/scripts/hiddenapi/signature_trie.py b/scripts/hiddenapi/signature_trie.py
new file mode 100644
index 0000000..f2176f5
--- /dev/null
+++ b/scripts/hiddenapi/signature_trie.py
@@ -0,0 +1,252 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2022 The Android Open Source Project
+#
+# 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.
+"""Verify that one set of hidden API flags is a subset of another."""
+
+from itertools import chain
+
+
+# pylint: disable=line-too-long
+class InteriorNode:
+    """An interior node in a trie.
+
+    Each interior node has a dict that maps from an element of a signature to
+    either another interior node or a leaf. Each interior node represents either
+    a package, class or nested class. Class members are represented by a Leaf.
+
+    Associating the set of flags [public-api] with the signature
+    "Ljava/lang/Object;->String()Ljava/lang/String;" will cause the following
+    nodes to be created:
+    Node()
+    ^- package:java -> Node()
+       ^- package:lang -> Node()
+           ^- class:Object -> Node()
+              ^- member:String()Ljava/lang/String; -> Leaf([public-api])
+
+    Associating the set of flags [blocked,core-platform-api] with the signature
+    "Ljava/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;"
+    will cause the following nodes to be created:
+    Node()
+    ^- package:java -> Node()
+       ^- package:lang -> Node()
+           ^- class:Character -> Node()
+              ^- class:UnicodeScript -> Node()
+                 ^- member:of(I)Ljava/lang/Character$UnicodeScript;
+                    -> Leaf([blocked,core-platform-api])
+
+    Attributes:
+        nodes: a dict from an element of the signature to the Node/Leaf
+          containing the next element/value.
+    """
+
+    # pylint: enable=line-too-long
+
+    def __init__(self):
+        self.nodes = {}
+
+    # pylint: disable=line-too-long
+    @staticmethod
+    def signature_to_elements(signature):
+        """Split a signature or a prefix into a number of elements:
+
+        1. The packages (excluding the leading L preceding the first package).
+        2. The class names, from outermost to innermost.
+        3. The member signature.
+        e.g.
+        Ljava/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;
+        will be broken down into these elements:
+        1. package:java
+        2. package:lang
+        3. class:Character
+        4. class:UnicodeScript
+        5. member:of(I)Ljava/lang/Character$UnicodeScript;
+        """
+        # Remove the leading L.
+        #  - java/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;
+        text = signature.removeprefix("L")
+        # Split the signature between qualified class name and the class member
+        # signature.
+        #  0 - java/lang/Character$UnicodeScript
+        #  1 - of(I)Ljava/lang/Character$UnicodeScript;
+        parts = text.split(";->")
+        member = parts[1:]
+        # Split the qualified class name into packages, and class name.
+        #  0 - java
+        #  1 - lang
+        #  2 - Character$UnicodeScript
+        elements = parts[0].split("/")
+        packages = elements[0:-1]
+        class_name = elements[-1]
+        if class_name in ("*", "**"):  # pylint: disable=no-else-return
+            # Cannot specify a wildcard and target a specific member
+            if len(member) != 0:
+                raise Exception(f"Invalid signature {signature}: contains "
+                                f"wildcard {class_name} and "
+                                f"member signature {member[0]}")
+            wildcard = [class_name]
+            # Assemble the parts into a single list, adding prefixes to identify
+            # the different parts.
+            #  0 - package:java
+            #  1 - package:lang
+            #  2 - *
+            return list(chain(["package:" + x for x in packages], wildcard))
+        else:
+            # Split the class name into outer / inner classes
+            #  0 - Character
+            #  1 - UnicodeScript
+            classes = class_name.split("$")
+            # Assemble the parts into a single list, adding prefixes to identify
+            # the different parts.
+            #  0 - package:java
+            #  1 - package:lang
+            #  2 - class:Character
+            #  3 - class:UnicodeScript
+            #  4 - member:of(I)Ljava/lang/Character$UnicodeScript;
+            return list(
+                chain(["package:" + x for x in packages],
+                      ["class:" + x for x in classes],
+                      ["member:" + x for x in member]))
+
+    # pylint: enable=line-too-long
+
+    def add(self, signature, value):
+        """Associate the value with the specific signature.
+
+        :param signature: the member signature
+        :param value: the value to associated with the signature
+        :return: n/a
+        """
+        # Split the signature into elements.
+        elements = self.signature_to_elements(signature)
+        # Find the Node associated with the deepest class.
+        node = self
+        for element in elements[:-1]:
+            if element in node.nodes:
+                node = node.nodes[element]
+            else:
+                next_node = InteriorNode()
+                node.nodes[element] = next_node
+                node = next_node
+        # Add a Leaf containing the value and associate it with the member
+        # signature within the class.
+        last_element = elements[-1]
+        if not last_element.startswith("member:"):
+            raise Exception(
+                f"Invalid signature: {signature}, does not identify a "
+                "specific member")
+        if last_element in node.nodes:
+            raise Exception(f"Duplicate signature: {signature}")
+        node.nodes[last_element] = Leaf(value)
+
+    def get_matching_rows(self, pattern):
+        """Get the values (plural) associated with the pattern.
+
+        e.g. If the pattern is a full signature then this will return a list
+        containing the value associated with that signature.
+
+        If the pattern is a class then this will return a list containing the
+        values associated with all members of that class.
+
+        If the pattern is a package then this will return a list containing the
+        values associated with all the members of all the classes in that
+        package and sub-packages.
+
+        If the pattern ends with "*" then the preceding part is treated as a
+        package and this will return a list containing the values associated
+        with all the members of all the classes in that package.
+
+        If the pattern ends with "**" then the preceding part is treated
+        as a package and this will return a list containing the values
+        associated with all the members of all the classes in that package and
+        all sub-packages.
+
+        :param pattern: the pattern which could be a complete signature or a
+        class, or package wildcard.
+        :return: an iterable containing all the values associated with the
+        pattern.
+        """
+        elements = self.signature_to_elements(pattern)
+        node = self
+
+        # Include all values from this node and all its children.
+        selector = lambda x: True
+
+        last_element = elements[-1]
+        if last_element in ("*", "**"):
+            elements = elements[:-1]
+            if last_element == "*":
+                # Do not include values from sub-packages.
+                selector = lambda x: not x.startswith("package:")
+
+        for element in elements:
+            if element in node.nodes:
+                node = node.nodes[element]
+            else:
+                return []
+        return chain.from_iterable(node.values(selector))
+
+    def values(self, selector):
+        """:param selector: a function that can be applied to a key in the nodes
+
+        attribute to determine whether to return its values.
+
+        :return: A list of iterables of all the values associated with
+        this node and its children.
+        """
+        values = []
+        self.append_values(values, selector)
+        return values
+
+    def append_values(self, values, selector):
+        """Append the values associated with this node and its children.
+
+        For each item (key, child) in nodes the child node's values are returned
+        if and only if the selector returns True when called on its key. A child
+        node's values are all the values associated with it and all its
+        descendant nodes.
+
+        :param selector: a function that can be applied to a key in the nodes
+        attribute to determine whether to return its values.
+        :param values: a list of a iterables of values.
+        """
+        for key, node in self.nodes.items():
+            if selector(key):
+                node.append_values(values, lambda x: True)
+
+
+class Leaf:
+    """A leaf of the trie
+
+    Attributes:
+        value: the value associated with this leaf.
+    """
+
+    def __init__(self, value):
+        self.value = value
+
+    def values(self, selector):  # pylint: disable=unused-argument
+        """:return: A list of a list of the value associated with this node."""
+        return [[self.value]]
+
+    def append_values(self, values, selector):  # pylint: disable=unused-argument
+        """Appends a list of the value associated with this node to the list.
+
+        :param values: a list of a iterables of values.
+        """
+        values.append([self.value])
+
+
+def signature_trie():
+    return InteriorNode()