+ Common header to all I2NP messages, which contains important information like an checksum, expiration date, etc. +
++ 1 byte Integer specifying the type of this message, followed by an 4 byte Integer specifying the message-id. After that there is an expiration Date, followed by an 2 byte Integer specifying the length of the message payload, followed by an Hash, which is truncated to the first byte. After that the actual message data follows. +
{% filter escape %}
++----+----+----+----+----+
+|type| msg-id |
+----+----+----+----+----+----+----+----+
-|type| msg-id | expiration
+| expiration |
+----+----+----+----+----+----+----+----+
- date | size |chks|
-+----+----+----+----+----+----+----+----+
-| data .....
-+----+---//
+| size |chks|
++----+----+----+
{% endfilter %}
{% filter escape %}
-type:
- 1 byte
- identifies the message type(see table below)
+type :: Integer
+ length -> 1 byte
+
+ purpose -> identifies the message type(see table below)
-msg-id:
- 4 bytes
- uniquely identifies this message(for some time at least)
+msg-id :: Integer
+ length -> 4 bytes
-expiration:
+ purpose -> uniquely identifies this message(for some time at least)
+
+expiration :: Date
8 bytes
date this message will expire
-size:
- 2 bytes
- length of the payload
+size :: Integer
+ length -> 2 bytes
+
+ purpose -> length of the payload
-chks:
- 1 byte
- checksum of the payload
- SHA256 hash truncated to the first byte
+chks :: Hash
+ length -> 1 byte
+
+ purpose -> checksum of the payload
+ SHA256 hash truncated to the first byte
-data:
- $size bytes
- actual message contents
+data :: Data
+ length -> $size bytes
+
+ purpose -> actual message contents
{% endfilter %}
+ One Record in a set of multiple records to request the creation of one hop in the tunnel. For more details see here. +
++ TunnelId to receive messages on, followed by the Hash of our RouterIdentity. After that the TunnelId and the Hash of the next router's RouterIdentity follow. +
+
{% filter escape %}
Cleartext:
+----+----+----+----+----+----+----+----+
-| receive tunnelId | local routerInfo |
-+----+----+----+----+ hash +
+| receive_tunnel | our_ident |
++----+----+----+----+ +
| |
+ +
| |
+ +
| |
+ +----+----+----+----+
-| | send tunnelId |
+| | next_tunnel |
+----+----+----+----+----+----+----+----+
-| nexthop routerInfo hash |
+| next_ident |
+ +
| |
+ +
@@ -78,7 +102,7 @@ Cleartext:
+ +
| |
+----+----+----+----+----+----+----+----+
-| AES256 tunnel layer key |
+| layer_key |
+ +
| |
+ +
@@ -86,7 +110,7 @@ Cleartext:
+ +
| |
+----+----+----+----+----+----+----+----+
-| AES256 tunnel IV key |
+| iv_key |
+ +
| |
+ +
@@ -94,7 +118,7 @@ Cleartext:
+ +
| |
+----+----+----+----+----+----+----+----+
-| AES256 reply key |
+| reply_key |
+ +
| |
+ +
@@ -102,13 +126,13 @@ Cleartext:
+ +
| |
+----+----+----+----+----+----+----+----+
-| reply IV |
+| reply_iv |
+ +
| |
-+----+----+----+----+----+----+----+----+
-|flag| request time | next msg-id
-+----+----+----+----+----+----+----+----+
- | padding...
++----+----+----+----+----+----+----+----+----+
+|flag| request_time | send_message_id |
++----+----+----+----+----+----+----+----+----+
+| padding...
+----+----+----+--//
encrypted:
@@ -127,23 +151,51 @@ encrypted:
{% filter escape %}
unencrypted:
- * bytes 0-3: tunnel ID to receive messages as
- * bytes 4-35: local router identity hash
- * bytes 36-39: next tunnel ID
- * bytes 40-71: next router identity hash
- * bytes 72-103: AES-256 tunnel layer key
- * bytes 104-135: AES-256 tunnel IV key
- * bytes 136-167: AES-256 reply key
- * bytes 168-183: reply IV
- * byte 184: flags
- * bytes 185-188: request time (in hours since the epoch)
- * bytes 189-192: next message ID
- * bytes 193-222: uninterpreted / random padding
-Taken from i2p.i2p/router/java/src/net/i2p/data/i2np/BuildRequestRecord.java
+
+receive_tunnel :: TunnelId
+ length -> 4 bytes
+our_ident :: Hash
+ length -> 32 bytes
+
+next_tunnel :: TunnelId
+ length -> 4 bytes
+
+next_ident :: Hash
+ length -> 32 bytes
+
+layer_key :: SessionKey
+ length -> 32 bytes
+
+iv_key :: SessionKey
+ length -> 32 bytes
+
+reply_key :: SessionKey
+ length -> 32 bytes
+
+reply_iv :: Integer
+ length -> 16 bytes
+
+flag :: Integer
+ length -> 1 byte
+
+request_time :: Integer
+ length -> 4 bytes
+
+send_message_id :: Integer
+ length -> 4 bytes
+
+padding :: Data
+ length -> 29 bytes
+
+ source -> random
encrypted:
-bytes 0-15: SHA-256-128(SHA256 hash truncated to 128bit) of the current hop's identity (the toPeer parameter)
-bytes 15-527: ElGamal-2048 encrypted block
+
+toPeer :: Hash
+ length -> 16 bytes
+
+encrypted_data :: ElGamal-2048 encrypted data
+ length -> 514
{% endfilter %}