diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..f6eceb0
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "oracle_javacard_sdks"]
+	path = oracle_javacard_sdks
+	url = https://github.com/martinpaljak/oracle_javacard_sdks.git
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..c1a0182
--- /dev/null
+++ b/README.md
@@ -0,0 +1,15 @@
+# Crystal
+
+Running Post-Quantum Cryptography (Kyber) on [JavaCard 2.2.1](https://www.cardlogix.com/product/cardlogix-credentsys-lite-java-card-72k/)
+
+## Setup
+
+This requires JDK 11 and Apache Ant to be installed with their environment variables set and `bin` directories added to the environment's `PATH`.
+
+Run this to setup the SDK environment:
+
+```bash
+git submodule update --init --recursive
+souce env
+ant setup
+```
diff --git a/build.xml b/build.xml
index d100482..e031590 100644
--- a/build.xml
+++ b/build.xml
@@ -4,13 +4,19 @@
     JavaCard Applet for the Kyber Post-Quantum-Cryptography Algorithm
   </description>
 
-  <property name="JCSDK" value="C:\Program Files (x86)\Oracle\Java Card Development Kit 3.0.5u4" />
+  <property name="JCSDK" value="./oracle_javacard_sdks/jc305u4_kit" />
 
   <target name="clean">
     <delete dir="build" />
   </target>
 
-  <target name="setup">
+  <target name="check.sdk">
+    <condition property="jcsdk.exists">
+      <available file="${JCSDK}" type="dir" />
+    </condition>
+  </target>
+
+  <target name="setup" depends="check.sdk" if="jcsdk.exists">
     <mkdir dir="tools"/>
     <get src="https://github.com/martinpaljak/ant-javacard/releases/download/v24.11.19/ant-javacard.jar" dest="tools" skipexisting="true"/>
     <get src="https://github.com/martinpaljak/GlobalPlatformPro/releases/download/v24.10.15/gp.jar" dest="tools" skipexisting="true"/>
@@ -20,7 +26,7 @@
     <!-- ant-javacard task from javacard.pro -->
     <taskdef name="javacard" classname="pro.javacard.ant.JavaCard" classpath="tools/ant-javacard.jar" />
     <javacard jckit="${JCSDK}">
-      <cap output="build/cyber.cap" aid="A000000648" sources="src" targetsdk="java_card_kit-2_2_1">
+      <cap output="build/cyber.cap" aid="A000000648" sources="src" targetsdk="./oracle_javacard_sdks/jc221_kit">
         <applet class="org.hacdc.cyber.Cyber" aid="A0000006482F0002" />
       </cap>
     </javacard>
diff --git a/env b/env
new file mode 100644
index 0000000..5e053fa
--- /dev/null
+++ b/env
@@ -0,0 +1,2 @@
+export JC_HOME="`pwd`/oracle_javacard_sdks/jc305u4_kit"
+export JC_CLASSIC_HOME="`pwd`/oracle_javacard_sdks/jc221_kit"
diff --git a/oracle_javacard_sdks b/oracle_javacard_sdks
new file mode 160000
index 0000000..e2df471
--- /dev/null
+++ b/oracle_javacard_sdks
@@ -0,0 +1 @@
+Subproject commit e2df471e04d86f33de69a947f44766fbef1d9d69