diff --git a/modules/apps/prebuilt.nix b/modules/apps/prebuilt.nix
index 4fa1dc9f..24c5a2e2 100644
--- a/modules/apps/prebuilt.nix
+++ b/modules/apps/prebuilt.nix
@@ -27,21 +27,6 @@ let
     include $(BUILD_PREBUILT)
     '');
 
-  build-tools =
-    (pkgs.androidPkgs.sdk (p: with p.stable; [ tools build-tools-30-0-2 ]))
-    + "/share/android-sdk/build-tools/30.0.2";
-
-  apksigner = pkgs.runCommand "apksigner" { nativeBuildInputs = [ pkgs.makeWrapper ]; } ''
-      mkdir -p $out/bin
-      makeWrapper "${pkgs.jre8_headless}/bin/java" "$out/bin/apksigner" \
-        --add-flags "-jar ${build-tools}/lib/apksigner.jar"
-    '';
-
-  signApk = {name, apk, keyPath}: pkgs.runCommand "${name}-signed.apk" { nativeBuildInputs = [ pkgs.jre8_headless ]; } ''
-    cp ${apk} $out
-    ${apksigner}/bin/apksigner sign --key ${keyPath}.pk8 --cert ${keyPath}.x509.pem $out
-  '';
-
   # TODO: Uses IFD. Try to avoid using this.
   apkFingerprint = apk: (import pkgs.runCommand "apk-fingerprint" { nativeBuildInputs = [ pkgs.jre8_headless ]; } ''
     fingerprint=$(keytool -printcert -jarfile ${apk} | grep "SHA256:" | tr --delete ':' | cut --delimiter ' ' --fields 3)
@@ -139,8 +124,8 @@ in
 
           # Uses the sandbox exception in /keys
           signedApk = mkDefault (
-            if config.certificate == "PRESIGNED" then config.apk else (signApk {
-              inherit (config) name apk;
+            if config.certificate == "PRESIGNED" then config.apk else (pkgs.signApk {
+              inherit (config) apk;
               keyPath = _config.build.sandboxKeyPath config.certificate;
             }));
 
@@ -172,7 +157,7 @@ in
 
           ### Check minSdkVersion, targetSdkVersion
           # TODO: Also check permissions?
-          MANIFEST_DUMP=$(${build-tools}/aapt2 d xmltree --file AndroidManifest.xml ${apk})
+          MANIFEST_DUMP=$(${pkgs.build-tools}/aapt2 d xmltree --file AndroidManifest.xml ${apk})
 
           # It would be better if we could convert it back into true XML and then select based on XPath
           MIN_SDK_VERSION=$(echo "$MANIFEST_DUMP" | grep minSdkVersion | cut -d= -f2)
diff --git a/modules/google.nix b/modules/google.nix
index d47e39ef..c8244f78 100644
--- a/modules/google.nix
+++ b/modules/google.nix
@@ -66,7 +66,10 @@ in
         config_priorityOnlyDndExemptPackages = [ "com.google.android.dialer" ]; # Found under PixelConfigOverlayCommon.apk
       };
       apps.prebuilt.GoogleDialer = {
-        apk = "${productPath}/priv-app/GoogleDialer/GoogleDialer.apk";
+        apk = pkgs.verifyApk {
+          apk = "${productPath}/priv-app/GoogleDialer/GoogleDialer.apk";
+          sha256 = "e2d049f3a01192f620b1240615fa8c13badc553c22bc6fddfca45c84d8fc545d";
+        };
         privileged = true;
         certificate = "PRESIGNED";
       };
@@ -77,40 +80,58 @@ in
       google.base.enable = true;
       google.dialer.enable = true;
       apps.prebuilt = {
-        Tycho = {
-          apk = "${productPath}/app/Tycho/Tycho.apk"; # Google Fi app
+        Tycho = { # Google Fi app
+          apk = pkgs.verifyApk {
+            apk = "${productPath}/app/Tycho/Tycho.apk";
+            sha256 = "4c36af4a5bdad97c1f3d8b283416d244496c2ac5eafe8226079ef6f676fd1859";
+          };
           certificate = "PRESIGNED";
         };
-        GCS = {
-          apk = "${productPath}/priv-app/GCS/GCS.apk"; # Google Connectivity Services (does wifi VPN at least)
+        GCS = { # Google Connectivity Services (does wifi VPN at least)
+          apk = pkgs.verifyApk {
+            apk = "${productPath}/priv-app/GCS/GCS.apk";
+            sha256 = "8efed9b84a6320eafde625cea7bb6bae0e320473d0e3c04fb0cd43b779078e1d";
+          };
           certificate = "PRESIGNED";
           privileged = true;
         };
 #### Disabling for now, since calls aren't working ####
 #        CarrierServices = {
-#          apk = "${productPath}/priv-app/CarrierServices/CarrierServices.apk"; # Google Carrier Services. com.google.android.ims (needed for wifi calls)
+#          apk = pkgs.verifyApk {
+#            apk = "${productPath}/priv-app/CarrierServices/CarrierServices.apk"; # Google Carrier Services. com.google.android.ims (needed for wifi calls)
+#            sha256 = "c25d5afacb6783109d6136d79353fad4f6541c3545d25228a18703d043ca783f";
+#          };
 #          certificate = "PRESIGNED";
 #          privileged = true;
 #        };
-        CarrierSettings = {
-          apk = "${productPath}/priv-app/CarrierSettings/CarrierSettings.apk"; # com.google.android.carrier
+        CarrierSettings = { # com.google.android.carrier
+          apk = pkgs.verifyApk {
+            apk = "${productPath}/priv-app/CarrierSettings/CarrierSettings.apk";
+            sha256 = "383d1e1b525ec6fb8204c5bf9b8390d37fd157e78b8b7212d61487b178066d20";
+          };
           certificate = "PRESIGNED";
           privileged = true;
         };
-        CarrierSetup = {
-          apk = "${systemExtPath}/priv-app/CarrierSetup/CarrierSetup.apk"; # com.google.android.carriersetup
+        CarrierSetup = { # com.google.android.carriersetup
+          apk = "${systemExtPath}/priv-app/CarrierSetup/CarrierSetup.apk"; # Uses device-specific keys
           certificate = "PRESIGNED";
           privileged = true;
         };
       } // (optionalAttrs (config.deviceFamily == "crosshatch") { # TODO: Generalize to other devices with esim
         EuiccGoogle = {
-          apk = "${productPath}/priv-app/EuiccGoogle/EuiccGoogle.apk";
+          apk = pkgs.verifyApk {
+            apk = "${productPath}/priv-app/EuiccGoogle/EuiccGoogle.apk";
+            sha256 = "7e26b6d5802a16799448ad635868f0345d6730310634684c0ae44e7e9f7ea764";
+          };
           certificate = "PRESIGNED";
           privileged = true;
         };
       }) // (optionalAttrs ((config.deviceFamily == "crosshatch") && (config.androidVersion >= 10)) {
         EuiccSupportPixel = {
-          apk = "${productPath}/priv-app/EuiccSupportPixel/EuiccSupportPixel.apk";
+          apk = pkgs.verifyApk {
+            apk = "${productPath}/priv-app/EuiccSupportPixel/EuiccSupportPixel.apk";
+            sha256 = "e0afeca77af15aee48a25ead314c576f8f274682a8fba3365610878f7c1ddb6b";
+          };
           certificate = "PRESIGNED";
           privileged = true;
         };
diff --git a/modules/microg.nix b/modules/microg.nix
index 53766ee3..889747b6 100644
--- a/modules/microg.nix
+++ b/modules/microg.nix
@@ -4,6 +4,10 @@ with lib;
 
 let
   version = "0.2.13.203915";
+  verifyApk = apk: pkgs.verifyApk {
+    inherit apk;
+    sha256 = "9bd06727e62796c0130eb6dab39b73157451582cbd138e86c468acc395d14165"; # O=NOGAPPS Project, C=DE
+  };
 in
 {
   options = {
@@ -27,10 +31,10 @@ in
     # Used https://github.com/lineageos4microg/android_prebuilts_prebuiltapks as source for Android.mk options
     apps.prebuilt = {
       GmsCore = { 
-        apk = pkgs.fetchurl {
+        apk = verifyApk (pkgs.fetchurl {
           url = "https://github.com/microg/android_packages_apps_GmsCore/releases/download/v${version}/GmsCore-v${version}.apk";
           sha256 = "0266zbmf20z7sa4xbgkq6f3qglrf8kcl24p6d87bzygm72340wxa";
-        };
+        });
         packageName = "com.google.android.gms";
         privileged = true;
         privappPermissions = [ "FAKE_PACKAGE_SIGNATURE" "INSTALL_LOCATION_PROVIDER" "CHANGE_DEVICE_IDLE_TEMP_WHITELIST" "UPDATE_APP_OPS_STATS" ];
@@ -38,16 +42,16 @@ in
         allowInPowerSave = true;
       };
 
-      GsfProxy.apk = pkgs.fetchurl {
+      GsfProxy.apk = verifyApk (pkgs.fetchurl {
         url = "https://github.com/microg/android_packages_apps_GsfProxy/releases/download/v0.1.0/GsfProxy.apk";
         sha256 = "14ln6i1qg435x223x3vndd608mra19d58yqqhhf6mw018cbip2c6";
-      };
+      });
 
       FakeStore = {
-        apk = pkgs.fetchurl {
+        apk = verifyApk (pkgs.fetchurl {
           url = "https://github.com/microg/android_packages_apps_FakeStore/releases/download/v0.1.0/FakeStore-v0.1.0.apk";
           sha256 = "1kp5v4qajp4cdx8pxw6j4776bcwc9f8jgfpiyllpk1kbhq92w1ci";
-        };
+        });
         packageName = "com.android.vending";
         privileged = true;
         privappPermissions = [ "FAKE_PACKAGE_SIGNATURE" ];
diff --git a/pkgs/build-tools/default.nix b/pkgs/build-tools/default.nix
new file mode 100644
index 00000000..d174db59
--- /dev/null
+++ b/pkgs/build-tools/default.nix
@@ -0,0 +1,42 @@
+{ lib, runCommand, androidPkgs, makeWrapper, jre8_headless }:
+
+let
+  # getName snippet originally from nixpkgs/pkgs/build-support/trivial-builders.nix
+  getName = fname: apk:
+    if lib.elem (builtins.typeOf apk) [ "path" "string" ]
+      then lib.removeSuffix ".apk" (builtins.baseNameOf apk)
+      else
+        if builtins.isAttrs apk && builtins.hasAttr "name" apk
+        then lib.removeSuffix ".apk" apk.name
+        else throw "${fname}: please supply a `name` argument because a default name can only be computed when the `apk` is a path or is an attribute set with a `name` attribute.";
+
+  build-tools =
+    (androidPkgs.sdk (p: with p.stable; [ tools build-tools-30-0-2 ]))
+    + "/share/android-sdk/build-tools/30.0.2";
+
+  apksigner = runCommand "apksigner" { nativeBuildInputs = [ makeWrapper ]; } ''
+      mkdir -p $out/bin
+      makeWrapper "${jre8_headless}/bin/java" "$out/bin/apksigner" \
+        --add-flags "-jar ${build-tools}/lib/apksigner.jar"
+    '';
+
+  signApk = { apk, keyPath, name ? (getName "signApk" apk) + "-signed.apk" }: runCommand name {} ''
+      cp ${apk} $out
+      ${apksigner}/bin/apksigner sign --key ${keyPath}.pk8 --cert ${keyPath}.x509.pem $out
+    '';
+
+  # Currently only supports 1 signer.
+  verifyApk = { apk, sha256, name ? (getName "verifyApk" apk) + ".apk" }: runCommand name {} ''
+    sha256=$(${apksigner}/bin/apksigner verify --print-certs ${apk} | grep "^Signer #1 certificate SHA-256 digest: " | cut -d" " -f6 || exit 1)
+
+    if [[ "$sha256" = "${sha256}" ]]; then
+      echo "${name} APK certificate digest matches ${sha256}"
+      ln -s ${apk} $out
+    else
+      echo "${name} APK certificate digest $sha256 is not ${sha256}"
+      exit 1
+    fi
+  '';
+in {
+  inherit build-tools apksigner signApk verifyApk;
+}
diff --git a/pkgs/default.nix b/pkgs/default.nix
index 2c82c028..116a180d 100644
--- a/pkgs/default.nix
+++ b/pkgs/default.nix
@@ -43,6 +43,14 @@ let
     fetchgerritpatchset = super.callPackage ./fetchgerritpatchset {};
 
     nix-prefetch-git = super.callPackage ./nix-prefetch-git {};
+
+    ###
+
+    inherit (super.callPackage ./build-tools {})
+      build-tools
+      apksigner
+      signApk
+      verifyApk;
   };
 in
   import nixpkgs (args // {