Add HMAC spec and links to SSU

HMAC and IV clarifications
NTCP formatting cleanups

i2p2www/pages/site/docs/spec/ssu.html

@@ -27,13 +27,16 @@ payload encrypted with the appropriate key.  The MAC used is
 HMAC-MD5, truncated to 16 bytes, while the key is a full 32 byte AES256 
 key.  The specific construct of the MAC is the first 16 bytes from:</p>
 <pre>
-  HMAC-MD5(payload || IV || (payloadLength ^ protocolVersion), macKey)
+  HMAC-MD5(encryptedPayload + IV + (payloadLength ^ protocolVersion), macKey)
 </pre>
-where '||' means append.
-The payload is the message starting with the flag byte.
+where '+' means append and '^' means exclusive-or.
+</p><p>
+The IV is generated randomly for each packet.
+The encryptedPayload is the encrypted version of the message starting with the flag byte (encrypt-then-MAC).
+The payloadLength used in the MAC is a 2 byte unsigned integer.
+Note that protocolVersion is 0, so the exclusive-or is a no-op.
 The macKey is either the introduction key or is constructed from the
 exchanged DH key (see details below), as specified for each message below.
-Note that protocolVersion is 0, so the exclusive or is a no-op.
 <b>WARNING</b> - the HMAC-MD5-128 used here is non-standard,
 see <a href="{{ site_url('docs/how/cryptography') }}#udp">the cryptography page</a> for details.
 
@@ -41,14 +44,38 @@ see <a href="{{ site_url('docs/how/cryptography') }}#udp">the cryptography page<
 <p>The payload itself (that is, the message starting with the flag byte)
 is AES256/CBC encrypted with the IV and the 
 sessionKey, with replay prevention addressed within its body, 
-explained below.  The payloadLength in the MAC is a 2 byte unsigned 
-integer.</p>
+explained below.
+</p>
   
 <p>The protocolVersion is a 2 byte unsigned integer
 and is currently set to 0.  Peers using a different protocol version will
 not be able to communicate with this peer, though earlier versions not
 using this flag are.</p>
 
+<h3>HMAC Specification</h3>
+<ul><li>
+Inner padding: 0x36...
+</li><li>
+Outer padding: 0x5C...
+</li><li>
+Key: 32 bytes
+</li><li>
+Hash digest function: MD5, 16 bytes
+</li><li>
+Block size: 64 bytes
+</li><li>
+MAC size: 16 bytes
+</li><li>
+Example C implementations:
+hmac.h in <a href="https://github.com/orignal/i2pd">i2pd</a>
+and
+I2PHMAC.cpp in <a href="https://github.com/i2pcpp/i2pcpp">i2pcpp</a>.
+</li><li>
+Example Java implementation:
+I2PHMac.java in <a href="https://github.com/i2p/i2p.i2p">i2p</a>
+</li></ul>
+
+
 <h3>Session Key Details</h3>
 The 32-byte session key is created as follows:
 <ol><li>

i2p2www/pages/site/docs/transport/ntcp.html

@@ -95,6 +95,7 @@ Alice                   contacts                      Bob
 {% endhighlight %}
 
 <pre>
+
   {% trans %}Legend:{% endtrans %}
     X, Y: {% trans %}256 byte DH public keys{% endtrans %}
     H(): 32 byte SHA256 Hash
@@ -163,7 +164,7 @@ Alice sends Bob:
     {% trans %}Size:{% endtrans %} 288 bytes
 {% endhighlight %}
 <p>{% trans %}Contents:{% endtrans %}</p>
-{% highlight %}
+{% highlight lang='dataspec' %}
  +----+----+----+----+----+----+----+----+
  |         X, as calculated from DH      |
  +                                       +
@@ -182,6 +183,7 @@ Alice sends Bob:
 {% endhighlight %}
 
 <pre>
+
   X: {% trans %}256 byte X from Diffie Hellman{% endtrans %}
 
   HXxorHI:  {% trans commonstructures=site_url('docs/spec/common-structures') -%}
@@ -231,6 +233,7 @@ This is the DH reply. Bob sends Alice:
 {% endhighlight %}
 
 <pre>
+
   Y: {% trans %}256 byte Y from Diffie Hellman{% endtrans %}
 
   HXY:  {% trans %}SHA256 Hash(X concatenated with Y){% endtrans %}
@@ -243,7 +246,7 @@ This is the DH reply. Bob sends Alice:
 
 
 <p>{% trans %}Encrypted Contents:{% endtrans %}</p>
-{% highlight %}
+{% highlight lang='dataspec' %}
  +----+----+----+----+----+----+----+----+
  |         Y as calculated from DH       |
  +                                       +
@@ -266,6 +269,7 @@ This is the DH reply. Bob sends Alice:
 {% endhighlight %}
 
 <pre>
+
   Y: {% trans %}256 byte Y from Diffie Hellman{% endtrans %}
 
   encrypted data: {% trans cryptography=site_url('docs/how/cryptography') -%}
@@ -291,7 +295,7 @@ This contains Alice's router identity, and a DSA signature of the critical data.
     {% trans %}Size:{% endtrans %} 448 bytes (typ. for 387 byte identity)
 {% endhighlight %}
 <p>{% trans %}Unencrypted Contents:{% endtrans %}</p>
-{% highlight %}
+{% highlight lang='dataspec' %}
  +----+----+----+----+----+----+----+----+
  |   sz    | Alice's Router Identity     |
  +----+----+                             +
@@ -318,6 +322,7 @@ This contains Alice's router identity, and a DSA signature of the critical data.
 {% endhighlight %}
 
 <pre>
+
   sz: {% trans %}2 byte size of Alice's router identity to follow (should always be 387){% endtrans %}
 
   ident: {% trans commonstructures=site_url('docs/spec/common-structures') -%}
@@ -337,7 +342,7 @@ the 40 byte <a href="{{ commonstructures }}#type_Signature">DSA signature</a> of
 </pre>
 
 <p>{% trans %}Encrypted Contents:{% endtrans %}</p>
-{% highlight %}
+{% highlight lang='dataspec' %}
  +----+----+----+----+----+----+----+----+
  |                                       |
  +                                       +
@@ -348,6 +353,7 @@ the 40 byte <a href="{{ commonstructures }}#type_Signature">DSA signature</a> of
 {% endhighlight %}
 
 <pre>
+
   encrypted data: {% trans cryptography=site_url('docs/how/cryptography') -%}
 448 bytes <a href="{{ cryptography }}#AES">AES encrypted</a> using the DH session key and
                   the last 16 bytes of HXxorHI (i.e., the last 16 bytes of message #1) as the IV
@@ -381,7 +387,7 @@ This is a DSA signature of the critical data. Bob sends Alice:
     {% trans %}Size:{% endtrans %} 48 bytes
 {% endhighlight %}
 <p>{% trans %}Unencrypted Contents:{% endtrans %}</p>
-{% highlight %}
+{% highlight lang='dataspec' %}
  +----+----+----+----+----+----+----+----+
  |                                       |
  +                                       +
@@ -398,6 +404,7 @@ This is a DSA signature of the critical data. Bob sends Alice:
 {% endhighlight %}
 
 <pre>
+
   signature: {% trans commonstructures=site_url('docs/spec/common-structures') -%}
 the 40 byte <a href="{{ commonstructures }}#type_Signature">DSA signature</a> of the following concatenated data:
              X, Y, Alice's <a href="{{ commonstructures }}#struct_RouterIdentity">Router Identity</a>, tsA, tsB.
@@ -410,7 +417,7 @@ the 40 byte <a href="{{ commonstructures }}#type_Signature">DSA signature</a> of
 
 
 <p>{% trans %}Encrypted Contents:{% endtrans %}</p>
-{% highlight %}
+{% highlight lang='dataspec' %}
  +----+----+----+----+----+----+----+----+
  |                                       |
  +                                       +
@@ -421,6 +428,7 @@ the 40 byte <a href="{{ commonstructures }}#type_Signature">DSA signature</a> of
 {% endhighlight %}
 
 <pre>
+
   encrypted data: {% trans cryptography=site_url('docs/how/cryptography') -%}
 48 bytes <a href="{{ cryptography }}#AES">AES encrypted</a> using the DH session key and
                   the last 16 bytes of the encrypted contents of message #2 as the IV