Add spongy castle sources to libraries folder

libraries/spongycastle/jce/src/main/java/javax/crypto/SecretKey.java

@@ -0,0 +1,28 @@
+package javax.crypto;
+
+import java.security.Key;
+
+/**
+ * A secret (symmetric) key.
+ * <p>
+ * This interface contains no methods or constants.
+ * Its only purpose is to group (and provide type safety for) secret keys.
+ * <p>
+ * Provider implementations of this interface must overwrite the
+ * <code>equals</code> and <code>hashCode</code> methods inherited from
+ * <code>java.lang.Object</code>, so that secret keys are compared based on
+ * their underlying key material and not based on reference.
+ * <p>
+ * Keys that implement this interface return the string <code>RAW</code>
+ * as their encoding format (see <code>getFormat</code>), and return the
+ * raw key bytes as the result of a <code>getEncoded</code> method call. (The
+ * <code>getFormat</code> and <code>getEncoded</code> methods are inherited
+ * from the <code>java.security.Key</code> parent interface.)
+ *
+ * @see SecretKeyFactory
+ * @see Cipher
+ */
+public abstract interface SecretKey
+    extends Key
+{
+}