diff --git a/Libraries/libcar/Headers/car/AttributeList.h b/Libraries/libcar/Headers/car/AttributeList.h
index 3de361abc..297c30e93 100644
--- a/Libraries/libcar/Headers/car/AttributeList.h
+++ b/Libraries/libcar/Headers/car/AttributeList.h
@@ -75,6 +75,13 @@ class AttributeList {
         size_t count,
         uint32_t const *identifiers) const;
 
+    /*
+     * Write an attribute list into an a vector of bytes using the identifier
+     * order in keyfmt->identifiers.
+     */
+    std::vector<uint8_t> write(
+        car_key_format const *keyfmt) const;
+
 public:
     /*
      * Print debugging information about the list.
@@ -90,6 +97,14 @@ class AttributeList {
         uint32_t const *identifiers,
         uint16_t const *values);
 
+    /*
+     * Load an attribute list from packed struct car_key_format members and
+     * a car_rendition_key buffer.
+     */
+    static AttributeList Load(
+        car_key_format const *keyfmt,
+        car_rendition_key const *values);
+
     /*
      * Load an attribute list from a buffer of identifier value pairs.
      */
diff --git a/Libraries/libcar/Sources/AttributeList.cpp b/Libraries/libcar/Sources/AttributeList.cpp
index 1aff336c3..d164b5d3c 100644
--- a/Libraries/libcar/Sources/AttributeList.cpp
+++ b/Libraries/libcar/Sources/AttributeList.cpp
@@ -66,6 +66,16 @@ Load(size_t count, uint32_t const *identifiers, uint16_t const *values)
     return AttributeList(attributes);
 }
 
+AttributeList AttributeList::
+Load(car_key_format const *keyfmt, car_rendition_key const *values)
+{
+    std::unordered_map<enum car_attribute_identifier, uint16_t> attributes;
+    for (size_t i = 0; i < keyfmt->num_identifiers; ++i) {
+        attributes.insert({ (enum car_attribute_identifier)keyfmt->identifier_list[i], values[i] });
+    }
+    return AttributeList(attributes);
+}
+
 AttributeList AttributeList::
 Load(size_t count, struct car_attribute_pair const *pairs)
 {
@@ -95,3 +105,20 @@ write(size_t count, uint32_t const *identifiers) const
     return output;
 }
 
+std::vector<uint8_t> AttributeList::
+write(car_key_format const *keyfmt) const
+{
+    std::vector<uint8_t> output = std::vector<uint8_t>(sizeof(uint16_t) * keyfmt->num_identifiers);
+    uint16_t *values = reinterpret_cast<uint16_t *>(output.data());
+    std::unordered_map<enum car_attribute_identifier, uint16_t> attributes;
+    for (size_t i = 0; i < keyfmt->num_identifiers; ++i) {
+        enum car_attribute_identifier identifier = (enum car_attribute_identifier) keyfmt->identifier_list[i];
+        auto result = _values.find(identifier);
+        if (result != _values.end()) {
+            values[i] = result->second;
+        } else {
+            values[i] = 0;
+        }
+    }
+    return output;
+}
diff --git a/Libraries/libcar/Sources/Reader.cpp b/Libraries/libcar/Sources/Reader.cpp
index 2e39db6a1..c92cf95ae 100644
--- a/Libraries/libcar/Sources/Reader.cpp
+++ b/Libraries/libcar/Sources/Reader.cpp
@@ -82,7 +82,7 @@ renditionIterate(std::function<void(Rendition const &)> const &iterator) const
         KeyValuePair kv = (KeyValuePair)it.second;
         car_rendition_key *rendition_key = (car_rendition_key *)kv.key;
         struct car_rendition_value *rendition_value = (struct car_rendition_value *)kv.value;
-        AttributeList attributes = AttributeList::Load(keyfmt->num_identifiers, keyfmt->identifier_list, rendition_key);
+        AttributeList attributes = AttributeList::Load(keyfmt, rendition_key);
         Rendition rendition = Rendition::Load(attributes, rendition_value);
         iterator(rendition);
     }
@@ -264,7 +264,7 @@ lookupRenditions(Facet const &facet) const
         KeyValuePair value = (KeyValuePair)it->second;
         car_rendition_key *rendition_key = (car_rendition_key *)value.key;
         struct car_rendition_value *rendition_value = (struct car_rendition_value *)value.value;
-        AttributeList attributes = AttributeList::Load(keyfmt->num_identifiers, keyfmt->identifier_list, rendition_key);
+        AttributeList attributes = AttributeList::Load(keyfmt, rendition_key);
         Rendition rendition = Rendition::Load(attributes, rendition_value);
         result.push_back(rendition);
     }
diff --git a/Libraries/libcar/Sources/Writer.cpp b/Libraries/libcar/Sources/Writer.cpp
index 3bcbafd5e..400f0877b 100644
--- a/Libraries/libcar/Sources/Writer.cpp
+++ b/Libraries/libcar/Sources/Writer.cpp
@@ -162,7 +162,7 @@ write() const
     bom_tree_reserve(renditions_tree_context, rendition_count);
     if (renditions_tree_context != NULL) {
         for (auto const &item : _renditions) {
-            auto attributes_value = item.second.attributes().write(keyfmt->num_identifiers, keyfmt->identifier_list);
+            auto attributes_value = item.second.attributes().write(keyfmt);
             auto rendition_value = item.second.write();
             bom_tree_add(
                 renditions_tree_context,