diff --git a/android/build.gradle b/android/build.gradle
index 7378a48..bbc8f69 100644
--- a/android/build.gradle
+++ b/android/build.gradle
@@ -31,7 +31,6 @@ apply plugin: 'com.android.library'
 
 android {
     compileSdkVersion 21
-    buildToolsVersion '26.0.2'
 
     defaultConfig {
         minSdkVersion 18
diff --git a/android/external/Makefile b/android/external/Makefile
index a6f21ff..a829ba3 100644
--- a/android/external/Makefile
+++ b/android/external/Makefile
@@ -281,6 +281,7 @@ curl-install: $(LOCAL)/lib/libcurl.so
 # using released package instead
 libiconv-1.14.tar.gz:
 	wget https://ftp.gnu.org/pub/gnu/libiconv/libiconv-1.14.tar.gz
+	sha256sum -c libiconv-1.14.tar.gz.sha256
 
 libiconv.src.stamp: libiconv-1.14.tar.gz
 	tar xvfz libiconv-1.14.tar.gz
@@ -420,7 +421,7 @@ libetpan-cleanzip:
 # using released package from debian. official ftp wasn't available today
 ossp-uuid_1.6.2.orig.tar.gz:
 	wget http://http.debian.net/debian/pool/main/o/ossp-uuid/ossp-uuid_1.6.2.orig.tar.gz
-	md5sum -c ossp-uuid_1.6.2.orig.tar.gz.md5
+	sha256sum -c ossp-uuid_1.6.2.orig.tar.gz.sha256
 
 uuid.src.stamp: ossp-uuid_1.6.2.orig.tar.gz
 	tar xvfz ossp-uuid_1.6.2.orig.tar.gz
diff --git a/android/external/libiconv-1.14.tar.gz.sha256 b/android/external/libiconv-1.14.tar.gz.sha256
new file mode 100644
index 0000000..c717b8b
--- /dev/null
+++ b/android/external/libiconv-1.14.tar.gz.sha256
@@ -0,0 +1 @@
+72b24ded17d687193c3366d0ebe7cde1e6b18f0df8c55438ac95be39e8a30613  libiconv-1.14.tar.gz
diff --git a/android/external/ossp-uuid_1.6.2.orig.tar.gz.md5 b/android/external/ossp-uuid_1.6.2.orig.tar.gz.md5
deleted file mode 100644
index 84b832e..0000000
--- a/android/external/ossp-uuid_1.6.2.orig.tar.gz.md5
+++ /dev/null
@@ -1 +0,0 @@
-5db0d43a9022a6ebbbc25337ae28942f  ossp-uuid_1.6.2.orig.tar.gz
diff --git a/android/external/ossp-uuid_1.6.2.orig.tar.gz.sha256 b/android/external/ossp-uuid_1.6.2.orig.tar.gz.sha256
new file mode 100644
index 0000000..c717b8b
--- /dev/null
+++ b/android/external/ossp-uuid_1.6.2.orig.tar.gz.sha256
@@ -0,0 +1 @@
+72b24ded17d687193c3366d0ebe7cde1e6b18f0df8c55438ac95be39e8a30613  libiconv-1.14.tar.gz