diff --git a/apex/apex.go b/apex/apex.go
index 68d9cb8..619ac33 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -75,6 +75,7 @@
 	executableTag = dependencyTag{name: "executable"}
 	javaLibTag    = dependencyTag{name: "javaLib"}
 	prebuiltTag   = dependencyTag{name: "prebuilt"}
+	keyTag        = dependencyTag{name: "key"}
 )
 
 func init() {
@@ -172,6 +173,9 @@
 
 	// List of prebuilt files that are embedded inside this APEX bundle
 	Prebuilts []string
+
+	// Name of the apex_key module that provides the private key to sign APEX
+	Key *string
 }
 
 type apexBundle struct {
@@ -185,14 +189,6 @@
 }
 
 func (a *apexBundle) DepsMutator(ctx android.BottomUpMutatorContext) {
-	// Native shared libs are added for all architectures of the device
-	// i.e., native_shared_lib_modules: ["libc"] adds both 64 and 32 variation
-	// of the module
-	arches := ctx.DeviceConfig().Arches()
-	if len(arches) == 0 {
-		panic("device build with no primary arch")
-	}
-
 	for _, arch := range ctx.MultiTargets() {
 		// Use *FarVariation* to be able to depend on modules having
 		// conflicting variations with this module. This is required since
@@ -208,16 +204,21 @@
 			{Mutator: "arch", Variation: arch.String()},
 			{Mutator: "image", Variation: "core"},
 		}, executableTag, a.properties.Binaries...)
-
-		ctx.AddFarVariationDependencies([]blueprint.Variation{
-			{Mutator: "arch", Variation: "android_common"},
-		}, javaLibTag, a.properties.Java_libs...)
-
-		ctx.AddFarVariationDependencies([]blueprint.Variation{
-			{Mutator: "arch", Variation: "android_common"},
-		}, prebuiltTag, a.properties.Prebuilts...)
 	}
 
+	ctx.AddFarVariationDependencies([]blueprint.Variation{
+		{Mutator: "arch", Variation: "android_common"},
+	}, javaLibTag, a.properties.Java_libs...)
+
+	ctx.AddFarVariationDependencies([]blueprint.Variation{
+		{Mutator: "arch", Variation: "android_common"},
+	}, prebuiltTag, a.properties.Prebuilts...)
+
+	if String(a.properties.Key) == "" {
+		ctx.ModuleErrorf("key is missing")
+		return
+	}
+	ctx.AddDependency(ctx.Module(), keyTag, String(a.properties.Key))
 }
 
 func getCopyManifestForNativeLibrary(cc *cc.Module) (fileToCopy android.Path, dirInApex string) {
@@ -259,34 +260,52 @@
 	// files to copy -> dir in apex
 	copyManifest := make(map[android.Path]string)
 
+	var keyFile android.Path
+
 	ctx.WalkDeps(func(child, parent android.Module) bool {
 		if _, ok := parent.(*apexBundle); ok {
 			// direct dependencies
 			depTag := ctx.OtherModuleDependencyTag(child)
+			depName := ctx.OtherModuleName(child)
 			switch depTag {
 			case sharedLibTag:
 				if cc, ok := child.(*cc.Module); ok {
 					fileToCopy, dirInApex := getCopyManifestForNativeLibrary(cc)
 					copyManifest[fileToCopy] = dirInApex
 					return true
+				} else {
+					ctx.PropertyErrorf("native_shared_libs", "%q is not a cc_library or cc_library_shared module", depName)
 				}
 			case executableTag:
 				if cc, ok := child.(*cc.Module); ok {
 					fileToCopy, dirInApex := getCopyManifestForExecutable(cc)
 					copyManifest[fileToCopy] = dirInApex
 					return true
+				} else {
+					ctx.PropertyErrorf("binaries", "%q is not a cc_binary module", depName)
 				}
 			case javaLibTag:
 				if java, ok := child.(*java.Library); ok {
 					fileToCopy, dirInApex := getCopyManifestForJavaLibrary(java)
 					copyManifest[fileToCopy] = dirInApex
 					return true
+				} else {
+					ctx.PropertyErrorf("java_libs", "%q is not a java_library module", depName)
 				}
 			case prebuiltTag:
 				if prebuilt, ok := child.(*android.PrebuiltEtc); ok {
 					fileToCopy, dirInApex := getCopyManifestForPrebuiltEtc(prebuilt)
 					copyManifest[fileToCopy] = dirInApex
 					return true
+				} else {
+					ctx.PropertyErrorf("prebuilts", "%q is not a prebuilt_etc module", depName)
+				}
+			case keyTag:
+				if key, ok := child.(*apexKey); ok {
+					keyFile = key.private_key_file
+					return false
+				} else {
+					ctx.PropertyErrorf("key", "%q is not an apex_key module", depName)
 				}
 			}
 		} else {
@@ -330,8 +349,6 @@
 
 	manifest := android.PathForModuleSrc(ctx, proptools.StringDefault(a.properties.Manifest, "manifest.json"))
 	fileContexts := android.PathForModuleSrc(ctx, proptools.StringDefault(a.properties.File_contexts, "file_contexts"))
-	// TODO(b/114488804) make this customizable
-	key := android.PathForSource(ctx, "system/apex/apexer/testdata/testkey.pem")
 
 	a.outputFile = android.PathForModuleOut(ctx, a.ModuleBase.Name()+apexSuffix)
 
@@ -351,7 +368,7 @@
 		copyCommands = append(copyCommands, "cp "+src.String()+" "+dest_path)
 	}
 	implicitInputs := append(android.Paths(nil), filesToCopy...)
-	implicitInputs = append(implicitInputs, cannedFsConfig, manifest, fileContexts, key)
+	implicitInputs = append(implicitInputs, cannedFsConfig, manifest, fileContexts, keyFile)
 	outHostBinDir := android.PathForOutput(ctx, "host", ctx.Config().PrebuiltOS(), "bin").String()
 	prebuiltSdkToolsBinDir := filepath.Join("prebuilts", "sdk", "tools", runtime.GOOS, "bin")
 	ctx.ModuleBuild(pctx, android.ModuleBuildParams{
@@ -365,7 +382,7 @@
 			"manifest":         manifest.String(),
 			"file_contexts":    fileContexts.String(),
 			"canned_fs_config": cannedFsConfig.String(),
-			"key":              key.String(),
+			"key":              keyFile.String(),
 		},
 	})
 
@@ -382,6 +399,7 @@
 			fmt.Fprintln(w, "LOCAL_PREBUILT_MODULE_FILE :=", a.outputFile.String())
 			fmt.Fprintln(w, "LOCAL_MODULE_PATH :=", filepath.Join("$(OUT_DIR)", a.installDir.RelPathString()))
 			fmt.Fprintln(w, "LOCAL_INSTALLED_MODULE_STEM :=", name+apexSuffix)
+			fmt.Fprintln(w, "LOCAL_REQUIRED_MODULES :=", String(a.properties.Key))
 			fmt.Fprintln(w, "include $(BUILD_PREBUILT)")
 		}}
 }
diff --git a/apex/key.go b/apex/key.go
new file mode 100644
index 0000000..ff348a8
--- /dev/null
+++ b/apex/key.go
@@ -0,0 +1,88 @@
+// Copyright (C) 2018 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.
+
+package apex
+
+import (
+	"fmt"
+	"io"
+
+	"android/soong/android"
+	"github.com/google/blueprint/proptools"
+)
+
+var String = proptools.String
+
+func init() {
+	android.RegisterModuleType("apex_key", apexKeyFactory)
+}
+
+type apexKey struct {
+	android.ModuleBase
+
+	properties apexKeyProperties
+
+	public_key_file  android.Path
+	private_key_file android.Path
+
+	keyName string
+}
+
+type apexKeyProperties struct {
+	// Path to the public key file in avbpubkey format. Installed to the device.
+	// Base name of the file is used as the ID for the key.
+	Public_key *string
+	// Path to the private key file in pem format. Used to sign APEXs.
+	Private_key *string
+}
+
+func apexKeyFactory() android.Module {
+	module := &apexKey{}
+	module.AddProperties(&module.properties)
+	android.InitAndroidModule(module)
+	return module
+}
+
+func (m *apexKey) DepsMutator(ctx android.BottomUpMutatorContext) {
+}
+
+func (m *apexKey) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+	m.public_key_file = android.PathForModuleSrc(ctx, String(m.properties.Public_key))
+	m.private_key_file = android.PathForModuleSrc(ctx, String(m.properties.Private_key))
+
+	pubKeyName := m.public_key_file.Base()[0 : len(m.public_key_file.Base())-len(m.public_key_file.Ext())]
+	privKeyName := m.private_key_file.Base()[0 : len(m.private_key_file.Base())-len(m.private_key_file.Ext())]
+
+	if pubKeyName != privKeyName {
+		ctx.ModuleErrorf("public_key %q (keyname:%q) and private_key %q (keyname:%q) do not have same keyname",
+			m.public_key_file.String(), pubKeyName, m.private_key_file, privKeyName)
+		return
+	}
+	m.keyName = pubKeyName
+
+	ctx.InstallFile(android.PathForModuleInstall(ctx, "etc/security/apex"), m.keyName, m.public_key_file)
+}
+
+func (m *apexKey) AndroidMk() android.AndroidMkData {
+	return android.AndroidMkData{
+		Class:      "ETC",
+		OutputFile: android.OptionalPathForPath(m.public_key_file),
+		Extra: []android.AndroidMkExtraFunc{
+			func(w io.Writer, outputFile android.Path) {
+				fmt.Fprintln(w, "LOCAL_MODULE_PATH :=", "$(TARGET_OUT)/etc/security/apex")
+				fmt.Fprintln(w, "LOCAL_INSTALLED_MODULE_STEM :=", m.keyName)
+			},
+		},
+	}
+}