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clarify crypto/hmac usage for simpler implementation

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jrandom
2005-04-05 15:28:54 +00:00
committed by zzz
parent 756a4e3995
commit 400feb3ba7
1 changed files with 23 additions and 16 deletions
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router/doc/udp.html
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@ -1,4 +1,4 @@
<code>$Id: udp.html,v 1.7 2005/03/29 19:20:07 jrandom Exp $</code>
<code>$Id: udp.html,v 1.8 2005/04/04 12:21:30 jrandom Exp $</code>
<h1>Secure Semireliable UDP (SSU)</h1>
<b>DRAFT</b>
@ -48,7 +48,8 @@ key. The specific construct of the MAC is the first 16 bytes from:</p>
<p>The payload itself is AES256/CBC encrypted with the IV and the
sessionKey, with replay prevention addressed within its body,
explained below.</p>
explained below. The payloadLength in the MAC is a 2 byte unsigned
integer in 2s complement.</p>
<h2><a name="payload">Payload</a></h2>
@ -136,14 +137,17 @@ around briefly, to address packet loss and reordering.</p>
<li>1 byte IP address size</li>
<li>that many byte representation of Alice's IP address</li>
<li>2 byte port number (unsigned, big endian 2s complement)</li>
<li>0-15 pad bytes to reach the 16 byte boundary</li>
<li>4 byte relay tag which Alice can publish (else 0x0)</li>
<li>40 byte DSA signature of the critical exchanged data</li>
<li>40 byte DSA signature of the critical exchanged data, encrypted
with another layer of encryption using the negotiated sessionKey.
The IV is reused here (but with the sessionKey, not the introKey).</li>
<li>8 bytes padding, encrypted with an additional layer of encryption
using the negotiated session key as part of the DSA block</li>
<li>N bytes, currently uninterpreted (later, for challenges)</li>
</ul></td></tr>
<tr><td align="right" valign="top"><b>Key used:</b></td>
<td>introKey for the data through the pad bytes, and the
sessionKey for the DSA signature</td></tr>
<td>introKey, with an additional layer of encryption over the 40 byte
signature and the following 8 bytes padding.</td></tr>
</table>
<pre>
@ -155,18 +159,21 @@ around briefly, to address packet loss and reordering.</p>
+----+----+----+----+----+----+----+----+
|size| that many byte IP address (4-16) |
+----+----+----+----+----+----+----+----+
| Port (A)| (pad to 16 byte boundary) |
| Port (A)| public relay tag | |
+----+----+----+----+----+----+ |
| DSA signature |
| |
| |
| |
| +----+----+
| |
+----+----+----+----+----+----+----+----+
| public relay tag | DSA signature |
+----+----+----+----+ |
(8 bytes of padding) | |
+----+----+----+----+----+----+ |
| arbitrary amount |
| of uninterpreted data |
. . .
| |
| |
| |
| |
+ +----+----+----+----+
| | arbitrary amount |
+----+----+----+----+ |
| of uninterpreted data |
+----+----+----+----+----+----+----+----+
</pre>