* Matthew Toseland <toad at amphibian.dyndns.org> [2007-10-24 16:23:10]:
> Comments below...
>
> What exactly is this key for? I believe it is for round trip verification ...
It is.
> does resetting it have any impact on forward secrecy?
When we rekey we have to flush the cache because it gets invalidated.
Granted we could flush the cache without rekeying... Flushing the
cache has an impact on forward secrecy.
>
> On Wednesday 24 October 2007 15:15, you wrote:
> > Author: nextgens
> > Date: 2007-10-24 14:15:17 +0000 (Wed, 24 Oct 2007)
> > New Revision: 15523
> >
> > Modified:
> > trunk/freenet/src/freenet/node/FNPPacketMangler.java
> > Log:
> > JFK:
> > Change the transient key on a regular basis (at least once every
> > 30mins).
> We need it to be deterministic if we want to have a strict PFS interval.
> >
> > Modified: trunk/freenet/src/freenet/node/FNPPacketMangler.java
> > ===================================================================
> > --- trunk/freenet/src/freenet/node/FNPPacketMangler.java 2007-10-24
> > 09:53:20
> UTC (rev 15522)
> > +++ trunk/freenet/src/freenet/node/FNPPacketMangler.java 2007-10-24
> > 14:15:17
> UTC (rev 15523)
> > - // The following is used in the HMAC calculation of JFK message3 and
> message4
> > + /** The following is used in the HMAC calculation of JFK message3 and
> message4 */
> > private static final byte[] JFK_PREFIX_INITIATOR, JFK_PREFIX_RESPONDER;
> > static {
> > byte[] I = null,R = null;
> > @@ -103,6 +100,21 @@
> > private static final int TRANSIENT_KEY_SIZE = HASH_LENGTH;
> > /** The key used to authenticate the hmac */
> > private final byte[] transientKey = new byte[TRANSIENT_KEY_SIZE];
> > + public static final int TRANSIENT_KEY_REKEYING_MIN_INTERVAL =
> > 30*60*1000;
> > + /** The Runnable in charge of rekeying on a regular basis */
> > + private final Runnable transitentKeyRekeyer = new Runnable() {
> > + public void run() {
> > + resetTransientKey();
> > +
> > + try {
> > + // Ugly hack to let the node start up. When we
> > are first
> > + // called in the constructor the ticker is not
> > available!
> > + while(!node.isHasStarted())
> > + Thread.sleep(1000);
> > + } catch (InterruptedException e) {}
> > + node.getTicker().queueTimedJob(transitentKeyRekeyer,
> TRANSIENT_KEY_REKEYING_MIN_INTERVAL);
> > + }
> > + };
>
> All you have to do is add a start() method to FNPPacketMangler, and have it
> called during the start() phase of the node (before PacketSender start).
> Include the initial scheduling of the above in that method.
>
> > /** Minimum headers overhead */
> > private static final int HEADERS_LENGTH_MINIMUM =
> > 4 + // sequence number
> > @@ -139,7 +151,10 @@
> > fullHeadersLengthMinimum = HEADERS_LENGTH_MINIMUM +
> sock.getHeadersLength();
> > fullHeadersLengthOneMessage = HEADERS_LENGTH_ONE_MESSAGE +
> sock.getHeadersLength();
> > logMINOR = Logger.shouldLog(Logger.MINOR, this);
> > - resetTransientKey();
> > +
> > + // Yeah there is a race condition... the key might be at 0 for
> > a while...
> > + // but it will get reset soonish and current runs will be
> > invalidated.
> > + node.executor.execute(transitentKeyRekeyer, "JFK
> > transientRekeyer");
> > }
>
> Should be in start(), *not* in FNPPM.
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