diff --git a/libs/libfabrickey/src/base/fabric_key.cpp b/libs/libfabrickey/src/base/fabric_key.cpp
index f9c84103d..0ae52b821 100644
--- a/libs/libfabrickey/src/base/fabric_key.cpp
+++ b/libs/libfabrickey/src/base/fabric_key.cpp
@@ -39,6 +39,20 @@ FabricKey::fabric_word_line_bank_range FabricKey::wl_banks(
                          wl_bank_ids_[region_id].end());
 }
 
+FabricKey::fabric_key_module_range FabricKey::modules() const {
+  return vtr::make_range(sub_key_module_ids_.begin(),
+                         sub_key_module_ids_.end());
+}
+
+FabricKey::fabric_sub_key_range FabricKey::sub_keys(
+  const FabricKeyModuleId& module_id) const {
+  VTR_ASSERT(valid_module_id(module_id));
+  return vtr::make_range(
+    sub_key_ids_.begin() + size_t(module_sub_keys_[module_id][0]),
+    sub_key_ids_.begin() + size_t(module_sub_keys_[module_id][0]) +
+      size_t(module_sub_keys_[module_id].size() - 1));
+}
+
 /************************************************************************
  * Public Accessors : Basic data query
  ***********************************************************************/
@@ -297,3 +311,13 @@ bool FabricKey::valid_wl_bank_id(const FabricRegionId& region_id,
   return (size_t(bank_id) < wl_bank_ids_[region_id].size()) &&
          (bank_id == wl_bank_ids_[region_id][bank_id]);
 }
+
+bool FabricKey::valid_module_id(const FabricKeyModuleId& module_id) const {
+  return (size_t(module_id) < sub_key_module_ids_.size()) &&
+         (module_id == sub_key_module_ids_[module_id]);
+}
+
+bool FabricKey::valid_sub_key_id(const FabricSubKeyId& sub_key_id) const {
+  return (size_t(sub_key_id) < sub_key_ids_.size()) &&
+         (sub_key_id == sub_key_ids_[sub_key_id]);
+}
diff --git a/libs/libfabrickey/src/base/fabric_key.h b/libs/libfabrickey/src/base/fabric_key.h
index 53c9f89ac..3089b8638 100644
--- a/libs/libfabrickey/src/base/fabric_key.h
+++ b/libs/libfabrickey/src/base/fabric_key.h
@@ -47,12 +47,18 @@ class FabricKey {
   typedef vtr::vector<FabricWordLineBankId,
                       FabricWordLineBankId>::const_iterator
     fabric_word_line_bank_iterator;
+  typedef vtr::vector<FabricSubKeyId, FabricSubKeyId>::const_iterator
+    fabric_sub_key_iterator;
+  typedef vtr::vector<FabricKeyModuleId, FabricKeyModuleId>::const_iterator
+    fabric_key_module_iterator;
   /* Create range */
   typedef vtr::Range<fabric_region_iterator> fabric_region_range;
   typedef vtr::Range<fabric_key_iterator> fabric_key_range;
   typedef vtr::Range<fabric_bit_line_bank_iterator> fabric_bit_line_bank_range;
   typedef vtr::Range<fabric_word_line_bank_iterator>
     fabric_word_line_bank_range;
+  typedef vtr::Range<fabric_sub_key_iterator> fabric_sub_key_range;
+  typedef vtr::Range<fabric_key_module_iterator> fabric_key_module_range;
 
  public: /* Constructors */
   FabricKey();
@@ -62,6 +68,8 @@ class FabricKey {
   fabric_region_range regions() const;
   fabric_bit_line_bank_range bl_banks(const FabricRegionId& region_id) const;
   fabric_word_line_bank_range wl_banks(const FabricRegionId& region_id) const;
+  fabric_key_module_range modules() const;
+  fabric_sub_key_range sub_keys(const FabricKeyModuleId& module_id) const;
 
  public: /* Public Accessors: Basic data query */
   /* Access all the keys of a region */
@@ -156,8 +164,11 @@ class FabricKey {
                         const FabricBitLineBankId& bank_id) const;
   bool valid_wl_bank_id(const FabricRegionId& region_id,
                         const FabricWordLineBankId& bank_id) const;
+  bool valid_module_id(const FabricKeyModuleId& module_id) const;
+  bool valid_sub_key_id(const FabricSubKeyId& sub_key_id) const;
 
  private: /* Internal data */
+  /* ---- Top-level keys and regions ---- */
   /* Unique ids for each region */
   vtr::vector<FabricRegionId, FabricRegionId> region_ids_;
 
@@ -199,6 +210,18 @@ class FabricKey {
   vtr::vector<FabricRegionId, vtr::vector<FabricWordLineBankId,
                                           std::vector<openfpga::BasicPort>>>
     wl_bank_data_ports_;
+
+  /* ---- List of sub modules ---- */
+  vtr::vector<FabricKeyModuleId, FabricKeyModuleId> sub_key_module_ids_;
+  vtr::vector<FabricKeyModuleId, std::string> sub_key_module_names_;
+  vtr::vector<FabricKeyModuleId, std::vector<FabricSubKeyId>> module_sub_keys_;
+  std::map<std::string, FabricKeyModuleId> module2subkey_lookup_;
+
+  /* ---- Sub keys ---- */
+  vtr::vector<FabricSubKeyId, FabricSubKeyId> sub_key_ids_;
+  vtr::vector<FabricSubKeyId, std::string> sub_key_names_;
+  vtr::vector<FabricSubKeyId, size_t> sub_key_values_;
+  vtr::vector<FabricSubKeyId, std::string> sub_key_alias_;
 };
 
 #endif
diff --git a/libs/libfabrickey/src/base/fabric_key_fwd.h b/libs/libfabrickey/src/base/fabric_key_fwd.h
index 0c282092f..628f849d4 100644
--- a/libs/libfabrickey/src/base/fabric_key_fwd.h
+++ b/libs/libfabrickey/src/base/fabric_key_fwd.h
@@ -16,11 +16,15 @@ struct fabric_region_id_tag;
 struct fabric_key_id_tag;
 struct fabric_bit_line_bank_id_tag;
 struct fabric_word_line_bank_id_tag;
+struct fabric_sub_key_id_tag;
+struct fabric_key_module_id_tag;
 
 typedef vtr::StrongId<fabric_region_id_tag> FabricRegionId;
 typedef vtr::StrongId<fabric_key_id_tag> FabricKeyId;
 typedef vtr::StrongId<fabric_bit_line_bank_id_tag> FabricBitLineBankId;
 typedef vtr::StrongId<fabric_word_line_bank_id_tag> FabricWordLineBankId;
+typedef vtr::StrongId<fabric_sub_key_id_tag> FabricSubKeyId;
+typedef vtr::StrongId<fabric_key_module_id_tag> FabricKeyModuleId;
 
 /* Short declaration of class */
 class FabricKey;