Encrypt logs on disk, store encryption key in DB.

bramble-api/src/main/java/org/briarproject/bramble/api/StringMap.java

@@ -1,8 +1,16 @@
 package org.briarproject.bramble.api;
 
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
 import java.util.Hashtable;
 import java.util.Map;
 
+import javax.annotation.Nullable;
+
+import static org.briarproject.bramble.util.StringUtils.fromHexString;
+import static org.briarproject.bramble.util.StringUtils.toHexString;
+
+@NotNullByDefault
 public abstract class StringMap extends Hashtable<String, String> {
 
 	protected StringMap(Map<String, String> m) {
@@ -52,4 +60,19 @@ public abstract class StringMap extends Hashtable<String, String> {
 	public void putLong(String key, long value) {
 		put(key, String.valueOf(value));
 	}
+
+	@Nullable
+	public byte[] getBytes(String key) {
+		String s = get(key);
+		if (s == null) return null;
+		try {
+			return fromHexString(s);
+		} catch (IllegalArgumentException e) {
+			return null;
+		}
+	}
+
+	public void putBytes(String key, byte[] value) {
+		put(key, toHexString(value));
+	}
 }

bramble-api/src/main/java/org/briarproject/bramble/api/crypto/StreamDecrypterFactory.java

@@ -19,4 +19,10 @@ public interface StreamDecrypterFactory {
 	 */
 	StreamDecrypter createContactExchangeStreamDecrypter(InputStream in,
 			SecretKey headerKey);
+
+	/**
+	 * Creates a {@link StreamDecrypter} for decrypting a log stream.
+	 */
+	StreamDecrypter createLogStreamDecrypter(InputStream in,
+			SecretKey headerKey);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/crypto/StreamEncrypterFactory.java

@@ -17,6 +17,12 @@ public interface StreamEncrypterFactory {
 	 * Creates a {@link StreamEncrypter} for encrypting a contact exchange
 	 * stream.
 	 */
-	StreamEncrypter createContactExchangeStreamDecrypter(OutputStream out,
+	StreamEncrypter createContactExchangeStreamEncrypter(OutputStream out,
+			SecretKey headerKey);
+
+	/**
+	 * Creates a {@link StreamEncrypter} for encrypting a log stream.
+	 */
+	StreamEncrypter createLogStreamEncrypter(OutputStream out,
 			SecretKey headerKey);
 }

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

@@ -16,8 +16,13 @@ public interface StreamReaderFactory {
 
 	/**
 	 * Creates an {@link InputStream InputStream} for reading from a contact
-	 * exchangestream.
+	 * exchange stream.
 	 */
 	InputStream createContactExchangeStreamReader(InputStream in,
 			SecretKey headerKey);
+
+	/**
+	 * Creates an {@link InputStream} for reading from a log stream.
+	 */
+	InputStream createLogStreamReader(InputStream in, SecretKey headerKey);
 }

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

@@ -9,15 +9,18 @@ import java.io.OutputStream;
 public interface StreamWriterFactory {
 
 	/**
-	 * Creates an {@link OutputStream OutputStream} for writing to a
-	 * transport stream
+	 * Creates a {@link StreamWriter} for writing to a transport stream.
 	 */
 	StreamWriter createStreamWriter(OutputStream out, StreamContext ctx);
 
 	/**
-	 * Creates an {@link OutputStream OutputStream} for writing to a contact
-	 * exchange stream.
+	 * Creates a {@link StreamWriter} for writing to a contact exchange stream.
 	 */
 	StreamWriter createContactExchangeStreamWriter(OutputStream out,
 			SecretKey headerKey);
+
+	/**
+	 * Creates a {@link StreamWriter} for writing to a log stream.
+	 */
+	StreamWriter createLogStreamWriter(OutputStream out, SecretKey headerKey);
 }