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we want to use E on the preIV, not HMAC - must be invertible (duh, thanks Connelly)

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adjusted preIV size accordingly, and definitely use a delivered layerIVKey
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jrandom
2005-01-19 06:24:25 +00:00
committed by zzz
parent a65e6c888c
commit f3b0e0cfc7
1 changed files with 4 additions and 7 deletions
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router/doc/tunnel-alt.html
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@ -1,4 +1,4 @@
<code>$Id: tunnel-alt.html,v 1.2 2005/01/18 11:01:55 jrandom Exp $</code>
<code>$Id: tunnel-alt.html,v 1.3 2005/01/18 11:21:12 jrandom Exp $</code>
<pre>
1) <a href="#tunnel.overview">Tunnel overview</a>
2) <a href="#tunnel.operation">Tunnel operation</a>
@ -140,7 +140,7 @@ preprocessed payload must be padded to a multiple of 16 bytes.</p>
<h3>2.2) <a name="tunnel.gateway">Gateway processing</a></h3>
<p>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.</p>
@ -155,13 +155,10 @@ the initial preprocessed data.</p>
<p>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.
<i>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
<i>What transform should be used - E(preIV, layerIVKey), where
we deliver an additional postprocessing layer key to each peer during the
<a href="#tunnel.request">tunnel creation</a> 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)?</i></p>
of the layerKey?</i></p>
<h3>2.3) <a name="tunnel.participant">Participant processing</a></h3>