Data: Check data length in typed constructors

Check for type match in KeyPair
Mark placeholder EncTypes 1-3 as unavailable

core/java/src/net/i2p/crypto/EncType.java

@@ -113,6 +113,9 @@ public enum EncType {
     private boolean x_isAvailable() {
         if (ELGAMAL_2048 == this)
             return true;
+        // EC types are placeholders for now
+        if (base == EncAlgo.EC)
+            return false;
         try {
             getParams();
         } catch (InvalidParameterSpecException e) {

core/java/src/net/i2p/crypto/KeyPair.java

@@ -13,9 +13,15 @@ public class KeyPair {
     private final PublicKey pub;
     private final PrivateKey priv;
 
+    /**
+     * @param publicKey non-null, same EncType as privateKey
+     * @param privateKey non-null, same EncType as publicKey
+     */
     public KeyPair(PublicKey publicKey, PrivateKey privateKey) {
         pub = publicKey;
         priv = privateKey;
+        if (pub.getType() != priv.getType())
+            throw new IllegalArgumentException();
     }
 
     public PublicKey getPublic() {

core/java/src/net/i2p/data/PrivateKey.java

@@ -53,11 +53,10 @@ public class PrivateKey extends SimpleDataStructure {
      *  @since 0.9.38
      */
     public PrivateKey(EncType type, byte data[]) {
-        super();
-        _type = type;
+        this(type);
         if (data == null)
             throw new IllegalArgumentException("Data must be specified");
-        _data = data;
+        setData(data);
     }
 
     /** constructs from base64

core/java/src/net/i2p/data/PublicKey.java

@@ -76,11 +76,10 @@ public class PublicKey extends SimpleDataStructure {
      *  @since 0.9.38
      */
     public PublicKey(EncType type, byte data[]) {
-        super();
-        _type = type;
+        this(type);
         if (data == null)
             throw new IllegalArgumentException("Data must be specified");
-        _data = data;
+        setData(data);
     }
 
     /** constructs from base64