Add abstract superclass for transport keys.

bramble-api/src/main/java/org/briarproject/bramble/api/transport/AbstractTransportKeys.java

@@ -0,0 +1,58 @@
+package org.briarproject.bramble.api.transport;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.TransportId;
+
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * Abstract superclass for {@link TransportKeys} and
+ * {@link StaticTransportKeys}.
+ */
+@Immutable
+@NotNullByDefault
+public abstract class AbstractTransportKeys {
+
+	private final TransportId transportId;
+	private final IncomingKeys inPrev, inCurr, inNext;
+	private final OutgoingKeys outCurr;
+
+	AbstractTransportKeys(TransportId transportId, IncomingKeys inPrev,
+			IncomingKeys inCurr, IncomingKeys inNext, OutgoingKeys outCurr) {
+		if (inPrev.getTimePeriod() != outCurr.getTimePeriod() - 1)
+			throw new IllegalArgumentException();
+		if (inCurr.getTimePeriod() != outCurr.getTimePeriod())
+			throw new IllegalArgumentException();
+		if (inNext.getTimePeriod() != outCurr.getTimePeriod() + 1)
+			throw new IllegalArgumentException();
+		this.transportId = transportId;
+		this.inPrev = inPrev;
+		this.inCurr = inCurr;
+		this.inNext = inNext;
+		this.outCurr = outCurr;
+	}
+
+	public TransportId getTransportId() {
+		return transportId;
+	}
+
+	public IncomingKeys getPreviousIncomingKeys() {
+		return inPrev;
+	}
+
+	public IncomingKeys getCurrentIncomingKeys() {
+		return inCurr;
+	}
+
+	public IncomingKeys getNextIncomingKeys() {
+		return inNext;
+	}
+
+	public OutgoingKeys getCurrentOutgoingKeys() {
+		return outCurr;
+	}
+
+	public long getTimePeriod() {
+		return outCurr.getTimePeriod();
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/transport/StaticTransportKeys.java

@@ -6,9 +6,13 @@ import org.briarproject.bramble.api.plugin.TransportId;
 
 import javax.annotation.concurrent.Immutable;
 
+/**
+ * Keys for communicating with a given contact over a given transport. Unlike
+ * {@link TransportKeys} these do not provide forward secrecy.
+ */
 @Immutable
 @NotNullByDefault
-public class StaticTransportKeys extends TransportKeys {
+public class StaticTransportKeys extends AbstractTransportKeys {
 
 	private final SecretKey rootKey;
 	private final boolean alice;

bramble-api/src/main/java/org/briarproject/bramble/api/transport/TransportKeys.java

@@ -6,52 +6,15 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import javax.annotation.concurrent.Immutable;
 
 /**
- * Keys for communicating with a given contact over a given transport.
+ * Keys for communicating with a given contact over a given transport. Unlike
+ * {@link StaticTransportKeys}, these keys provide forward secrecy.
  */
 @Immutable
 @NotNullByDefault
-public class TransportKeys {
+public class TransportKeys extends AbstractTransportKeys {
-
-	private final TransportId transportId;
-	private final IncomingKeys inPrev, inCurr, inNext;
-	private final OutgoingKeys outCurr;
 
 	public TransportKeys(TransportId transportId, IncomingKeys inPrev,
 			IncomingKeys inCurr, IncomingKeys inNext, OutgoingKeys outCurr) {
-		if (inPrev.getTimePeriod() != outCurr.getTimePeriod() - 1)
+		super(transportId, inPrev, inCurr, inNext, outCurr);
-			throw new IllegalArgumentException();
-		if (inCurr.getTimePeriod() != outCurr.getTimePeriod())
-			throw new IllegalArgumentException();
-		if (inNext.getTimePeriod() != outCurr.getTimePeriod() + 1)
-			throw new IllegalArgumentException();
-		this.transportId = transportId;
-		this.inPrev = inPrev;
-		this.inCurr = inCurr;
-		this.inNext = inNext;
-		this.outCurr = outCurr;
-	}
-
-	public TransportId getTransportId() {
-		return transportId;
-	}
-
-	public IncomingKeys getPreviousIncomingKeys() {
-		return inPrev;
-	}
-
-	public IncomingKeys getCurrentIncomingKeys() {
-		return inCurr;
-	}
-
-	public IncomingKeys getNextIncomingKeys() {
-		return inNext;
-	}
-
-	public OutgoingKeys getCurrentOutgoingKeys() {
-		return outCurr;
-	}
-
-	public long getTimePeriod() {
-		return outCurr.getTimePeriod();
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/crypto/KeyDerivationTestUtils.java

@@ -2,9 +2,9 @@ package org.briarproject.bramble.crypto;
 
 import org.briarproject.bramble.api.Bytes;
 import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.transport.AbstractTransportKeys;
 import org.briarproject.bramble.api.transport.IncomingKeys;
 import org.briarproject.bramble.api.transport.OutgoingKeys;
-import org.briarproject.bramble.api.transport.TransportKeys;
 
 import java.util.ArrayList;
 import java.util.HashSet;
@@ -16,9 +16,9 @@ import static org.junit.Assert.assertTrue;
 
 class KeyDerivationTestUtils {
 
-	static void assertAllDifferent(TransportKeys... transportKeys) {
+	static void assertAllDifferent(AbstractTransportKeys... transportKeys) {
 		List<SecretKey> secretKeys = new ArrayList<>();
-		for (TransportKeys k : transportKeys) {
+		for (AbstractTransportKeys k : transportKeys) {
 			secretKeys.add(k.getPreviousIncomingKeys().getTagKey());
 			secretKeys.add(k.getPreviousIncomingKeys().getHeaderKey());
 			secretKeys.add(k.getCurrentIncomingKeys().getTagKey());