Add KemUtil class

Author: peterdettman

tls/src/main/java/org/bouncycastle/tls/crypto/impl/jcajce/JcaTlsCrypto.java

@@ -1162,6 +1162,7 @@ protected Boolean isSupportedNamedGroup(int namedGroup)
             else if (NamedGroup.refersToASpecificKem(namedGroup))
             {
                 // TODO[tls-kem] When implemented via provider, need to check for support dynamically
+//                return Boolean.valueOf(KemUtil.isKemSupported(this, NamedGroup.getKemName(namedGroup)));
                 return Boolean.TRUE;
             }
             else if (NamedGroup.refersToAnECDSACurve(namedGroup))

tls/src/main/java/org/bouncycastle/tls/crypto/impl/jcajce/KemUtil.java

@@ -0,0 +1,27 @@
+package org.bouncycastle.tls.crypto.impl.jcajce;
+
+import javax.crypto.Cipher;
+
+class KemUtil
+{
+    static Cipher getCipher(JcaTlsCrypto crypto, String kemName)
+    {
+        try
+        {
+            return crypto.getHelper().createCipher(kemName);
+        }
+        catch (AssertionError e)
+        {
+            return null;
+        }
+        catch (Exception e)
+        {
+            return null;
+        }
+    }
+
+    static boolean isKemSupported(JcaTlsCrypto crypto, String kemName)
+    {
+    	return kemName != null && getCipher(crypto, kemName) != null;
+    }
+}