From f3b0e0cfc7f1c33287a2b17fe3882e95be3853c1 Mon Sep 17 00:00:00 2001 From: jrandom Date: Wed, 19 Jan 2005 06:24:25 +0000 Subject: [PATCH] we want to use E on the preIV, not HMAC - must be invertible (duh, thanks Connelly) adjusted preIV size accordingly, and definitely use a delivered layerIVKey --- router/doc/tunnel-alt.html | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/router/doc/tunnel-alt.html b/router/doc/tunnel-alt.html index fce5c9102..66b0eb1e0 100644 --- a/router/doc/tunnel-alt.html +++ b/router/doc/tunnel-alt.html @@ -1,4 +1,4 @@ -$Id: tunnel-alt.html,v 1.2 2005/01/18 11:01:55 jrandom Exp $ +$Id: tunnel-alt.html,v 1.3 2005/01/18 11:21:12 jrandom Exp $ 
 1) Tunnel overview
 2) Tunnel operation
@@ -140,7 +140,7 @@ preprocessed payload must be padded to a multiple of 16 bytes.

 
2.2) Gateway processing

 
 
After the preprocessing of messages into a padded payload, the gateway builds
-a random 4 byte preIV value, iteratively encrypting it and the tunnel message as
+a random 16 byte preIV value, iteratively encrypting it and the tunnel message as
 necessary, selects the next message ID from its outbound PRNG, and forwards the tuple 
 {tunnelID, messageID, preIV, encrypted tunnel message} to the next hop.

 
@@ -155,13 +155,10 @@ the initial preprocessed data.

 
 
The preIV postprocessing should be a secure transform of the received value 
 with sufficient expansion to provide the full 16 byte IV necessary for AES256.  
-What transform should be used - HMAC-SHA256(preIV, layerKey), using bytes
-0:15 as the IV, passing on bytes 16-19 as the next step's preIV?  Should
+What transform should be used - E(preIV, layerIVKey), where
 we deliver an additional postprocessing layer key to each peer during the 
 tunnel creation to reduce the potential exposure
-of the layerKey?  Should we replace the 4 byte preIV with a full 16 byte preIV 
-(even though 4 bytes will likely provide a sufficient keyspace in which to
-operate, as a single tunnel pumping 100KBps would only use 60,000 IVs)?

+of the layerKey?

 
 
2.3) Participant processing